/Users/andrea/_magisterarbeit/korpus/clean/testkorpus/1/file2.html NN ----------------------------------------- : research NN papers NNS Volume NN 61 CD Part NN 6 CD Pages NP 568 CD 574 CD November NP 2005 CD Received VVD 8 CD August NP 2005 CD Accepted JJ 10 CD October NP 2005 CD International NP Union NP of IN Crystallography NN 2005 CD Ab NP initio NP structure NN determination NN using VVG dispersive JJ differences NNS from IN multiple JJ wavelength NN synchrotron NN radiation NN powder NN diffraction NN data NN John NP R NP . SENT Helliwell NP , , a DT Madeleine NP Helliwella NP and CC Richard NP H NP . SENT Jonesb NN aDepartment NN of IN Chemistry NN , , The DT University NP of IN Manchester NP , , Manchester NP M NP 13 CD 9 CD PL NP , , England NP , , and CC bLennard NP Jones NP Laboratories NPS , , School NP of IN Chemistry NN and CC Physics NN , , Keele NP University NP , , Keele NP , , Staffordshire NP ST NP 5 CD 5 CD BG NP , , EnglandCorrespondence NN e NN mail NN . SENT john NN . SENT helliwell NP manchester NP . SENT ac NNS . SENT uk NP The DT purpose NN of IN this DT paper NN and CC a DT test NN case NN study NN is VBZ to TO assess VV a DT method NN of IN ab NP initio NP structure NN solution NN from IN powder NN diffraction NN data NNS using VVG f NN difference NN techniques NNS . SENT A DT theoretical JJ foundation NN for IN the DT approach NN used VVN is VBZ first RB provided VVN . SENT Then RB , , with IN a DT test NN case NN nickel NN sulfate NN hexahydrate NN , , it PP is VBZ shown VVN that IN both CC the DT position NN of IN the DT anomalous JJ scatterer NN Ni NP can MD be VB determined VVN and CC the DT structure NN can MD be VB developed VVN in IN full JJ . SENT Specifically RB , , synchrotron NN radiation NN data NNS were VBD collected VVN at IN two CD wavelengths NNS close JJ to TO the DT K NP edge NN for IN Ni NP and CC three CD wavelengths NNS remote JJ from IN the DT Ni NP absorption NN edge NN , , at IN 1 CD . SENT 3 CD , , 1 CD . SENT 8 CD and CC 2 CD . SENT 16 CD . SENT These DT five CD wavelengths NNS then RB allowed VVD various JJ combinations NNS to TO be VB tried VVN to TO establish VV which WDT wavelength NN pairs NNS gave VVD the DT optimum JJ signal NN in IN the DT Patterson NP maps NNS using VVG dispersive JJ amplitude NN differences NNS . SENT The DT initial JJ phases NNS derived VVN from IN the DT metal NN atom NN position NN then RB allowed VVD the DT structure NN to TO be VB fully RB developed VVN by IN difference NN Fourier NP cycling NN . SENT The DT relevance NN of IN these DT developments NNS to TO structure VV solution NN possibilities NNS for IN proteins NNS via IN powder NN dispersive JJ difference NN data NNS is VBZ then RB outlined VVN . SENT Keywords NNS . SENT anomalous JJ scattering NN . SENT powder NN diffraction NN . SENT protein NN microcrystals NNS . SENT synchrotron NN radiation NN . SENT 1 LS . SENT Introduction NN Various JJ advances NNS have VHP been VBN made VVN in IN the DT field NN of IN ab NP initio NP structure NN solution NN from IN powder NN diffraction NN data NNS . SENT One CD significant JJ advance NN in IN the DT last JJ two CD decades NNS involves VVZ instrumentation NN for IN the DT use NN of IN finely RB collimated VVN synchrotron NN radiation NN where WRB better RBR resolved VVN powder NN lines NNS have VHP been VBN found VVN to TO be VB beneficial JJ in IN the DT structure NN solution NN of IN , , for IN example NN , , cimetidine NN Cernik NP et NP al NP . SENT , , 1991 CD . SENT A DT different JJ method NN involving VVG the DT use NN of IN variable JJ temperature NN measurements NNS to TO exploit VV anisotropic JJ thermal JJ expansion NN also RB reduced VVD the DT peak NN to TO peak VV overlap VV Shankland NP , , David NP Sivia NP , , 1997 CD . SENT There EX have VHP in IN addition NN been VBN advances NNS in IN structure NN solution NN methodology NN with IN powder NN data NNS , , e NN . SENT g NN . SENT use NN of IN Monte NP Carlo NP methods NNS Harris NP et CC al NP . SENT , , 1994 CD . SENT Tremayne NP et NP al NP . SENT , , 1997 CD , , simulated JJ annealing VVG David NP et FW al NP . SENT , , 1998 CD . SENT Pagola NP Stephens NP , , 2000 CD and CC genetic JJ algorithms NNS Shankland NP , , David NP Csoka NP , , 1997 CD . SENT Kariuki NP et NP al NP . SENT , , 1997 CD . SENT Despite IN these DT advances NNS , , ab NP initio NP structure NN solution NN from IN powder NN diffraction NN data NNS is VBZ still RB not RB routine JJ , , particularly RB for IN more JJR complex JJ structures NNS . SENT this DT is VBZ because IN , , generally RB , , there EX are VBP a DT significant JJ number NN of IN overlapping JJ reflections NNS , , in IN addition NN to TO the DT fact NN that IN Friedel NP pairs NNS of IN reflections NNS are VBP exactly RB coincident JJ . SENT Thus RB , , there EX tends VVZ to TO be VB an DT underdetermination NN of IN data NNS , , somewhat RB similar JJ to TO that DT seen VVN in IN macromolecular JJ crystallography NN , , where WRB the DT data NNS tend VVP to TO be VB weak JJ and CC therefore RB do VVP not RB routinely RB extend VV to TO atomic JJ resolution NN . SENT Indeed RB , , powder NN dispersive JJ differences NNS PDD NN may MD be VB of IN important JJ application NN in IN protein NN powder NN diffraction NN , , which WDT we PP explain VVP . SENT The DT so RB called VVN multiple JJ wavelength NN anomalous JJ dispersion NN MAD JJ method NN is VBZ now RB routinely RB employed VVN for IN the DT crystal NN structure NN solution NN of IN macromolecules NNS . SENT This DT exploits VVZ the DT changes NNS in IN the DT atomic JJ scattering NN factor NN that WDT take VVP place NN close NN to TO the DT absorption NN edges NNS of IN elements NNS , , owing VVG to TO the DT variation NN of IN f NN and CC f NN with IN wavelength NN , , where WRB the DT atomic JJ scattering NN factor NN is VBZ given VVN by IN and NP f SYM 0 CD is VBZ the DT basic JJ scattering NN factor NN of IN an DT atom NN and CC f NN and CC f NN are VBP its PP$ real JJ and CC imaginary JJ components NNS of IN the DT anomalous JJ scattering NN . SENT By IN tuning VVG to TO the DT absorption NN edge NN of IN a DT specific JJ element NN in IN a DT sample NN to TO stimulate VV the DT maximum JJ changes NNS in IN f NN , , it PP is VBZ possible JJ to TO induce VV differences NNS in IN reflection NN intensities NNS with IN wavelength NN , , similar JJ to TO those DT seen VVN with IN the DT isomorphous JJ replacement NN method NN see VVP e NN . SENT g NN . SENT Helliwell NP 1992 CD and CC Ramakrishnan NP Biou NP 1997 CD for IN such PDT a DT treatment NN . SENT Approximately RB a DT third JJ of IN all DT genes NNS are VBP thought VVN to TO code VV for IN metalloproteins NNS , , thus RB providing VVG an DT anomalous JJ scatterer NN in IN these DT cases NNS . SENT Alternatively RB , , selenomethionine NN substitution NN affords VVZ a DT protein NN production NN method NN , , which WDT has VHZ general JJ utility NN for IN MAD JJ via IN the DT Se NP K NP edge NN Hendrickson NP et NP al NP . SENT , , 1990 CD . SENT In IN the DT powder NN diffraction NN field NN , , Mitchell NP 1957 CD , , working VVG from IN Okaya NP Pepinsky NP 1956 CD , , derived VVN a DT two CD wavelength NN anomalous JJ dispersion NN formalism NN for IN use NN in IN crystal NN structure NN analysis NN and CC also RB mentioned VVN its PP$ application NN to TO powder NN diffraction NN . SENT Anomalous JJ difference NN powder NN methods NNS have VHP been VBN used VVN to TO provide VV a DT quantitative JJ and CC qualitative JJ analysis NN of IN Co NP 3 CD O NN 4 CD in IN the DT matrix NN of IN kaolinite NN Al NP 2 CD Si NP 2 CD O NP 5 CD OH UH 4 CD , , using VVG laboratory NN based VVN data NNS measured VVN at IN Co NP K NP and CC K NP wavelengths NNS Wood NP et CC al NP . SENT , , 1986 CD . SENT Prandl NP 1990 CD , , 1994 CD suggested VVD a DT difference NN method NN using VVG partial JJ Patterson NP densities NNS , , rather RB than IN the DT more RBR basic JJ dispersive JJ difference NN Patterson NP densities NNS , , for IN ab NP initio NP structure NN solution NN from IN powder NN diffraction NN data NNS , , which WDT was VBD tested VVN for IN SrSO NP 4 CD Burger NP et NP al NP . SENT , , 1998 CD . SENT Gu NP et NP al NP . SENT 2000 CD used VVN simulated JJ two CD wavelength NN X NN ray NN powder NN data NNS for IN C NP 14 CD H NN 20 CD O NN 2 CD N NP 2 CD HBr NP and CC direct JJ methods NNS to TO break VV the DT phase NN ambiguity NN . SENT they PP compared VVD the DT effectiveness NN of IN developing VVG the DT rest NN of IN the DT structure NN after IN finding VVG the DT anomalous JJ scatterer NN Br NN atom NN by IN their PP$ direct JJ method NN versus CC conventional JJ difference NN Fourier NP cycling NN . SENT a DT reduction NN in IN the DT number NN of IN iterations NNS by IN a DT factor NN of IN two CD was VBD observed VVN . SENT We PP offer VVP in IN this DT paper NN some DT different JJ approaches NNS for IN the DT PDD JJ case NN . SENT i NP We PP provide VVP a DT theoretical JJ basis NN derived VVN from IN protein NN crystallography NN , , specifically RB working VVG from IN Helliwell NP 1992 CD to TO locate VV the DT anomalous JJ scatterer NN positions NNS . SENT ii NNS More RBR generally RB , , the DT peak NN to TO peak VV overlap VV is VBZ relieved VVN by IN working VVG initially RB for IN structure NN solution NN with IN data NNS truncated VVN in IN resolution NN limit NN for IN both DT full JJ and CC difference NN powder NN diffraction NN patterns NNS . SENT iii NNS Additionally RB , , general JJ relief NN of IN the DT peak NN to TO peak VV overlap VV problem NN for IN the DT full JJ pattern NN is VBZ available JJ via IN use NN of IN softer JJR X NN rays NNS which WDT spreads VVZ out RP the DT lines NNS . SENT A DT wavelength NN as IN soft JJ as IN 1 CD . SENT 8 CD or CC even RB 2 CD would MD still RB allow VV , , in IN full JJ back JJ scattering NN mode NN , , diffraction NN data NNS to TO 0 CD . SENT 9 CD or CC 1 CD , , respectively RB , , to TO be VB recordable JJ . SENT This DT is VBZ tested VVN here RB . SENT A DT different JJ , , more RBR extreme JJ , , example NN of IN powder NN diffraction NN using VVG soft JJ , , 5 CD , , X NP rays NNS is VBZ described VVN by IN Cernik NP et CC al NP . SENT 2005 CD . SENT iv NP Our NP study NN also RB affords VVZ an DT investigation NN of IN which WDT wavelength NN pairs NNS in IN our PP$ experiment NN lead NN to TO optimal JJ PDD JJ results NNS . SENT v NN Overall RB , , PDD NP techniques NNS could MD be VB employed VVN to TO extract VV the DT signal NN from IN the DT anomalously RB scattering VVG atom NN of IN interest NN , , locating VVG the DT atom NN using VVG the DT Patterson NP method NN from IN dispersive JJ differences NNS and CC using VVG that IN as IN the DT initial JJ phase NN information NN . SENT Like IN the DT heavy JJ atom NN method NN in IN single JJ crystal NN work NN , , the DT rest NN of IN the DT structure NN could MD be VB determined VVN by IN difference NN Fourier NN techniques NNS to TO locate VV the DT non JJ anomalously RB scattering VVG atoms NNS . SENT vi NP The DT development NN of IN PDD NP is VBZ relevant JJ to TO protein NN crystal NN powder NN diffraction NN . SENT It PP has VHZ been VBN shown VVN by IN Von NP Dreele NP et CC al NP . SENT 2000 CD and CC Margiolaki NP et NP al NP . SENT 2005 CD that IN protein NN model NN refinement NN and CC molecular JJ replacement NN structure NN solution NN are VBP possible JJ with IN protein NN powder NN data NNS . SENT However RB , , structure NN solution NN from IN PDD JJ data NNS has VHZ potential JJ too RB . SENT there EX is VBZ the DT complication NN , , however RB , , compared VVN with IN the DT standard JJ protein NN crystallography NN MAD JJ method NN that WDT , , since IN F NN hkl NN and CC are VBP exactly RB overlapped VVN in IN powder NN patterns NNS , , there EX will MD be VB a DT phase NN ambiguity NN see VVP Fig NN . SENT 9 CD . SENT 11 CD in IN Helliwell NP , , 1992 CD . SENT The DT phase NN ambiguity NN for IN each DT reflection NN would MD have VH to TO be VB resolved VVN via IN other JJ information NN such JJ as IN by IN calculating VVG a DT map NN using VVG averaged VVN phases NNS and CC using VVG e NN . SENT g NN . SENT solvent JJ flattening VVG to TO improve VV the DT reflection NN phase NN estimations NNS . SENT This DT paper NN and CC test NN case NN study NN provides VVZ a DT foundation NN for IN PDD NP applicable JJ to TO many JJ absorption NN edges NNS , , to TO inorganics NNS and CC to TO proteins NNS containing VVG metals NNS or CC selenomethionine NN or CC xenon NN introduced VVN under IN high JJ pressure NN . SENT 2 LS . SENT Theoretical JJ foundation NN for IN this DT paper NN Using VVG Fig NN . SENT 1 CD and CC the DT cosine NN rule NN , , we PP have VHP the DT following VVG equation NN . SENT where WRB L NP refers VVZ to TO the DT combined JJ scattering NN of IN the DT light JJ atom NN non JJ anomalous JJ scatterers NNS , , H NP refers VVZ to TO the DT heavy JJ atom NN scattering VVG anomalous JJ scatterer NN , , LH NP refers VVZ to TO the DT resultant JJ scattering NN of IN the DT light JJ and CC heavy JJ atoms NNS , , and CC the DT two CD wavelengths NNS used VVN are VBP 1 CD and CC 2 CD . SENT f SYM is VBZ the DT difference NN , , as IN a DT vector NN for IN the DT given VVN reflection NN , , due JJ to TO the DT two CD different JJ f NN values NNS of IN the DT anomalous JJ scatterer NN between IN these DT two CD wavelengths NNS . SENT Finally RB , , LH NP 2 CD and CC H NP are VBP the DT phase NN angles NNS of IN the DT structure NN factors NNS of IN the DT light JJ and CC heavy JJ atoms NNS at IN wavelength NN 2 CD and CC the DT heavy JJ atoms NNS alone RB , , respectively RB . SENT Note NN that IN Fig NN . SENT 1 CD is VBZ showing VVG vector NN quantities NNS but CC in IN the DT derivation NN here RB we PP refer VVP to TO the DT amplitudes NNS of IN those DT vector NN quantities NNS . SENT Figure NN 1 CD Argand NP diagram NN showing VVG the DT contribution NN of IN light JJ atoms NNS FL NP and CC the DT normal JJ scattering NN of IN the DT anomalous JJ scatterer NN atoms NNS FHo NP with IN a DT stimulated VVN wavelength NN dispersive JJ effect NN f SYM . SENT Point NP B NP represents VVZ an DT average NN of IN the DT Friedel NP reflection NN pairs NNS at IN 2 CD , , and CC , , and CC likewise RB for IN point NN C NP at IN 1 CD , , owing VVG to TO the DT superposition NN of IN Friedel NP reflections NNS in IN powder NN diffraction NN data NNS . SENT The DT angles NNS LH NP 2 CD and CC H NP are VBP respectively RB the DT angles NNS between IN the DT real JJ axis NN and CC OB NN for IN the DT former JJ and CC the DT real JJ axis NN and CC AD NN for IN the DT latter NN . SENT Then RB , , OA NP FL NP , , DC NP , , DB NP , , AD NN FHo NP , , CB NP , , OB NP FLH NP 2 CD , , OC NP FLH NP 1 CD . SENT We PP rearrange VV 1 CD as IN follows VVZ . SENT This DT is VBZ Since IN the DT purpose NN of IN our PP$ paper NN is VBZ to TO address VV the DT situation NN of IN extending VVG powder NN methods NNS to TO larger JJR unit NN cells NNS and CC correspondingly RB larger JJR structures NNS , , it PP is VBZ likely JJ that IN most JJS of IN the DT cases NNS will MD involve VV a DT relatively RB large JJ number NN of IN light JJ atoms NNS . SENT Hence RB we PP can MD make VV the DT approximation NN to TO 3 CD for IN the DT majority NN of IN the DT cases NNS that IN Also RB , , and CC 3 CD thus RB becomes VVZ Equation NN 6 CD shows NNS that IN the DT measured VVN structure NN factor NN amplitudes NNS at IN each DT wavelength NN when WRB subtracted VVN one NN from IN the DT other JJ produces VVZ a DT signal NN that WDT , , in IN our PP$ approximation NN , , is VBZ derived VVN from IN the DT anomalously RB scattering VVG atom NN alone RB . SENT We PP see VVP in IN the DT analysis NN section NN below IN that DT , , even RB in IN the DT case NN here RB of IN one CD Ni NP atom NN in IN the DT presence NN of IN just RB 11 CD light JJ atoms NNS , , the DT Patterson NP function NN calculated VVN with IN coefficients NNS that WDT are VBP the DT left JJ hand NN side NN of IN equation NN 6 CD shows NNS predominantly RB Ni NP atom NN self NN vectors NNS . SENT Prandl NP 1990 CD , , 1994 CD gives VVZ the DT exact JJ treatment NN , , where WRB he PP shows VVZ that DT use NN of IN simple JJ differences NNS in IN a DT Patterson NP synthesis NN , , i NP . SENT e SYM . SENT FLH NP 2 CD FLH NP 1 CD 2 CD also RB yields NNS cross VVP vectors NNS between IN the DT H NP and CC L NP atoms NNS . SENT this DT is VBZ also RB evident JJ from IN the DT right JJ hand NN sides NNS of IN equations NNS 1 CD 3 CD . SENT The DT above JJ treatment NN can MD be VB trivially RB extended VVN first JJ to TO the DT case NN of IN more JJR than IN one CD anomalously RB scattering VVG atom NN of IN the DT same JJ type NN . SENT In IN such PDT a DT case NN , , f NN in IN the DT above JJ equations NNS is VBZ a DT combined JJ vector NN , , which WDT is VBZ the DT collective JJ effect NN of IN the DT several JJ atoms NNS . SENT This DT is VBZ similar JJ to TO FL NP being NN a DT vector NN combined VVN from IN the DT vector NN contributions NNS of IN each DT and CC every DT light JJ atom NN . SENT The DT extension NN to TO the DT case NN of IN more JJR than IN one CD anomalously RB scattering VVG atom NN type NN , , whether IN of IN one CD or CC more JJR atoms NNS in IN each DT case NN , , is VBZ non JJ trivial JJ only RB in IN as RB much JJ as IN the DT two CD wavelengths NNS aiming VVG to TO stimulate VV a DT f NN for IN one CD atom NN type NN may MD be VB unable JJ to TO avoid VV or CC may MD deliberately RB seek VV to TO simultaneously RB have VH a DT f NN for IN two CD or CC more JJR atom NN types NNS and CC that IN a DT cross NN vector NN term NN occurs VVZ involving VVG the DT two CD atom NN types NNS see VVP Appendix NN 1 CD of IN Olczak NP et CC al NP . SENT , , 2003 CD . SENT Thus RB in IN such JJ situations NNS a DT Patterson NP map NN with IN coefficients NNS FLH NP 2 CD FLH NP 1 CD 2 CD would MD have VH self NN and CC cross NN vectors NNS between IN the DT various JJ anomalously RB scattering VVG atom NN types NNS and CC their PP$ constituent JJ atom NN populations NNS . SENT This DT is VBZ unlikely JJ to TO be VB a DT limiting VVG situation NN in IN that DT , , even RB with IN more JJR than IN one CD anomalous JJ scatterer NN type NN and CC each RB having VHG more JJR than IN one CD atom NN in IN each DT population NN , , the DT total JJ number NN of IN atoms NNS sought VVN from IN the DT Patterson NP is VBZ still RB very RB much RB less JJR than IN that DT in IN the DT native JJ Patterson NP , , i NP . SENT e SYM . SENT for IN the DT full JJ structure NN , , assuming VVG that IN the DT cross NN vectors VVZ to TO the DT light JJ atoms NNS are VBP weak JJ peaks NNS . SENT As RB stated VVN above RB , , the DT resolution NN of IN the DT data NNS can MD be VB truncated VVN to TO 1 CD . SENT 5 CD , , greatly RB reducing VVG the DT congestion NN of IN lines NNS . SENT From IN protein NN crystallography NN , , it PP is VBZ known VVN that IN relatively RB simple JJ partial JJ structures NNS of IN the DT anomalous JJ scatterers NNS are VBP derivable JJ from IN diffraction NN resolutions NNS significantly RB poorer JJR than IN atomic JJ resolution NN , , either CC by IN Patterson NP or CC direct JJ methods NNS using VVG anomalous JJ differences NNS Mukherjee NP et CC al NP . SENT , , 1989 CD . SENT On IN the DT theoretical JJ basis NN , , finally RB , , mention NN must MD be VB made VVN that IN a DT fundamental JJ limitation NN of IN the DT powder NN method NN remains VVZ even RB with IN a DT two CD wavelength NN approach NN . SENT i NP . SENT e SYM . SENT the DT hand NN of IN a DT molecule NN cannot NN be VB determined VVN because IN the DT Friedel NP equivalent NN reflections NNS exactly RB coincide VV . SENT In IN the DT protein NN case NN , , it PP is VBZ known VVN from IN the DT chemistry NN that WDT , , in IN nature NN , , amino NN acids NNS are VBP left VVN handed VVN , , this DT chemical NN property NN will MD be VB valuable JJ in IN structure NN determination NN re IN choice NN of IN the DT hand NN . SENT 3 LS . SENT Experimental JJ We PP have VHP chosen VVN a DT simple JJ compound NN as IN a DT test NN case NN , , namely RB nickel JJ sulfate NN hexahydrate NN Ni NP SO IN 4 CD 6 CD H NN 2 CD O NN . SENT the DT Ni NP atom NN K NP edge NN is VBZ well RB placed VVN for IN SR NN source NN powder NN instrumentation NN usage NN , , i NP . SENT e SYM . SENT in IN the DT mid JJ X NP ray NN wavelength NN range NN , , to TO allow VV reference NN test NN data NN sets VVZ to TO be VB collected VVN at IN shorter JJR and CC longer JJR wavelengths NNS . SENT This DT compound NN crystallizes VVZ in IN the DT tetragonal JJ space NN group NN P NN 41212 CD No RB . SENT 92 CD with IN a DT 6 CD . SENT 782 CD and CC c LS 18 CD . SENT 274 CD . SENT The DT literature NN value NN of IN the DT K NP absorption NN edge NN of IN Ni NP is VBZ 1 CD . SENT 4878 CD . SENT the DT position NN is VBZ expected VVN to TO be VB shifted VVN to TO higher JJR energy NN for IN Ni NP 2 CD by IN a DT few JJ eV NP . SENT The DT edge NN position NN of IN NiSO NP 4 CD 6 CD H NN 2 CD O NN was VBD determined VVN experimentally RB by IN fluorescence NN scans VVZ to TO be VB at IN 1 CD . SENT 4889 CD , , using VVG the DT flat JJ plate NN mode NN , , where WRB the DT f NN minimum NN was VBD assumed VVN to TO occur VV at IN a DT position NN half NN way NN up IN the DT edge NN . SENT Note NN that IN the DT oxidation NN state NN of IN nickel NN is VBZ II NP and CC the DT edge NN position NN should MD be VB about IN 4 CD eV NP shifted VVD to TO higher JJR energy NN , , i NP . SENT e SYM . SENT shorter JJR wavelength NN . SENT The DT value NN of IN 1 CD . SENT 4889 CD contains VVZ an DT angular JJ offset VV determined VVN during IN calibration NN of IN the DT machine NN Laundy NP et NP al NP . SENT , , 2003 CD . SENT Powder NN diffraction NN patterns NNS were VBD then RB collected VVN in IN capillary JJ mode NN . SENT A DT redetermination NN of IN the DT K NP edge NN position NN was VBD made VVN regularly RB at IN SRS NP reinjection NN , , and CC subsequent JJ absorption NN edge NN determinations NNS were VBD carried VVN out RP directly RB on IN the DT capillary NN mounted VVD sample NN . SENT Powder NN diffraction NN data NN sets NNS were VBD collected VVN at IN the NP f SYM dip NN at IN 1 CD . SENT 4889 CD , , the DT base NN of IN the DT edge NN at IN 1 CD . SENT 4912 CD as RB well RB as IN at IN 1 CD . SENT 7962 CD and CC 1 CD . SENT 3002 CD , , and CC finally RB at IN 2 CD . SENT 1608 CD . SENT The DT final JJ wavelength NN values NNS were VBD determined VVN by IN refining NN against IN the DT known VVN lattice NN parameters NNS for IN this DT compound NN for IN each DT data NNS set VVD Rousseau NP et NP al NP . SENT , , 2000 CD . SENT Measurements NNS were VBD made VVN to TO 120 CD in IN 2 CD , , except IN for IN the DT 2 CD . SENT 1608 CD data NNS , , where WRB data NNS were VBD collected VVN to TO 130 CD 2 CD . SENT The DT data NNS were VBD corrected VVN for IN beam NN decay NN using VVG the DT incident NN beam NN monitor NN . SENT Data NNS were VBD extracted VVN using VVG the DT Le NP Bail NP method NN Le NP Bail NP et CC al NP . SENT , , 1988 CD and CC using VVG GSAS NP Larson NP Von NP Dreele NP , , 1994 CD 1 CD . SENT 4889 CD , , wRp NP 0 CD . SENT 160 CD , , Rp NP 0 CD . SENT 124 CD . SENT 1 LS . SENT 4912 CD , , wRp NP 0 CD . SENT 073 CD , , Rp NP 0 CD . SENT 056 CD . SENT 1 LS . SENT 7962 CD , , wRp NP 0 CD . SENT 151 CD , , Rp NP 0 CD . SENT 109 CD . SENT 1 LS . SENT 3002 CD , , wRp NP 0 CD . SENT 074 CD , , Rp NP 0 CD . SENT 056 CD . SENT 2 LS . SENT 1608 CD , , wRp NP 0 CD . SENT 250 CD , , Rp NP 0 CD . SENT 192 CD . SENT In IN order NN to TO obtain VV a DT common JJ scaling NN for IN all PDT the DT data NNS , , the DT total JJ number NN of IN counts NNS Fo NP 2 CD for IN the DT first JJ 278 CD extracted VVN reflections NNS was VBD summed VVD , , except IN for IN the DT 2 CD . SENT 1608 CD data NN set NN , , which WDT used VVD the DT first JJ 185 CD reflections NNS . SENT Initial JJ scale NN factors NNS were VBD computed VVN to TO give VV each DT data NNS set VVD the DT same JJ number NN of IN counts NNS and CC applied VVN accordingly RB . SENT For IN the DT data NN set NN measured VVN at IN 1 CD . SENT 4912 CD , , the DT scale NN factor NN was VBD set VVN to TO one NN . SENT 4 LS . SENT Analyses NNS of IN the DT data NN sets VVZ The DT w NN 0 CD , , w NN and CC w NN sections NNS of IN the DT dispersive JJ difference NN Patterson NP maps NNS provide VVP discrimination NN between IN the DT various JJ wavelength NN pairs NNS assessed VVD , , since IN these DT should MD have VH the DT strongest JJS Ni NP Ni NP vectors VVZ , , at IN , , 0 CD . SENT 08 CD , , and CC 0 CD . SENT 420 CD . SENT 42 CD , , , , as RB well RB as IN the DT weaker JJR vectors NNS owing VVG to TO Ni NP S NP at IN 0 CD . SENT 5 CD , , 0 CD . SENT 5 CD , , 0 CD and CC 0 CD . SENT 08 CD , , 0 CD . SENT 08 CD , , Table NN 1 CD . SENT The DT calculated VVN peak NN heights NNS for IN each DT interatomic JJ vector NN have VHP been VBN assessed VVN by IN comparison NN with IN the DT native JJ structure NN calculated VVN Patterson NP by IN inspection NN . SENT Table NN 1 CD Details NNS of IN the DT Patterson NP self NN and CC cross NN vectors NNS for IN NiSO NP 4 CD 6 CD H NN 2 CD O NN a DT The NP coordinates VVZ of IN the DT atoms NNS in IN NiSO NP 4 CD . SENT 6 CD H NN 2 CD O NN . SENT Atom NN Position NN fractional JJ coordinates VVZ Ni NP 0 CD . SENT 71 CD , , 0 CD . SENT 71 CD , , 0 CD S NP 0 CD . SENT 21 CD , , 0 CD . SENT 21 CD , , 0 CD O NN 1 CD 0 CD . SENT 11 CD , , 0 CD . SENT 12 CD , , 0 CD . SENT 07 CD O NN 2 CD 0 CD . SENT 44 CD , , 0 CD . SENT 17 CD , , 0 CD . SENT 00 CD O NN 3 CD 0 CD . SENT 67 CD , , 0 CD . SENT 45 CD , , 0 CD . SENT 06 CD O NN 4 CD 0 CD . SENT 03 CD , , 0 CD . SENT 75 CD , , 0 CD . SENT 06 CD O NN 5 CD 0 CD . SENT 55 CD , , 0 CD . SENT 85 CD , , 0 CD . SENT 08 CD b SYM The DT Patterson NP peak NN positions NNS for IN the DT interatomic JJ vectors NNS in IN NiSO NP 4 CD . SENT 6 CD H NN 2 CD O NN the DT Patterson NP symmetry NN is VBZ P NN 4 CD mmm NNS . SENT Harker NP vectors VVZ u NN , , v NN , , w NN Expected VVD values NNS for IN Ni NP Expected VVN values NNS for IN S NP 2 CD x SYM , , 2 CD y NN , , 1 CD . SENT 42 CD , , 1 CD . SENT 42 CD , , 0 CD . SENT 42 CD , , 0 CD . SENT 42 CD , , , , 2 CD y NN , , 2 CD z SYM , , 1 CD . SENT 92 CD , , , , 0 CD . SENT 92 CD , , 2 CD y NN , , 2 CD x SYM , , 1 CD . SENT 42 CD , , 1 CD . SENT 42 CD 0 CD . SENT 42 CD , , 0 CD . SENT 42 CD , , , , 2 CD x SYM , , 2 CD z SYM , , 1 CD . SENT 92 CD , , , , 0 CD . SENT 92 CD , , Cross NP peaks NNS Position NN u NN , , v NN , , w NN Ni NP S NP 0 CD . SENT 5 CD , , 0 CD . SENT 5 CD , , 0 CD 0 CD . SENT 92 CD , , 0 CD . SENT 92 CD , , Ni NP O NP 1 CD 0 CD . SENT 60 CD , , 0 CD . SENT 59 CD , , 0 CD . SENT 07 CD Ni NP O NP 2 CD 0 CD . SENT 27 CD , , 0 CD . SENT 54 CD , , 0 CD Ni NP O NP 3 CD 0 CD . SENT 04 CD , , 0 CD . SENT 26 CD , , 0 CD . SENT 06 CD Ni NP O NP 4 CD 0 CD . SENT 68 CD , , 0 CD . SENT 04 CD , , 0 CD . SENT 06 CD Ni NP O NP 5 CD 0 CD . SENT 16 CD , , 0 CD . SENT 14 CD , , 0 CD . SENT 08 CD In IN order NN to TO calculate VV these DT maps NNS , , it PP was VBD necessary JJ to TO place VV each DT data NNS set VVN on IN a DT common JJ scale NN and CC this DT was VBD carried VVN out RP in IN two CD steps NNS . SENT Firstly RB , , account NN of IN the DT SRS NP ring NN current JJ decay NN was VBD applied VVN from IN ion NN chamber NN readings NNS , , as RB referred VVD to TO above RB . SENT The DT patterns NNS simply RB scaled VVN for IN beam NN current JJ decay NN are VBP given VVN in IN the DT supplementary JJ figures NNS as IN Le NP Bail NP extractions NNS . SENT 1 LS these DT do VVP show VV directly RB changes NNS in IN reflection NN intensities NNS and CC by IN comparison NN of IN the DT calculated VVN reflection NN intensities NNS that WDT are VBP particularly RB sensitive JJ to TO the DT Ni NP atom NN changes NNS in IN intensity NN can MD be VB ascribed VVN to TO the DT differences NNS in IN the DT Ni NP atom NN f SYM at IN the DT various JJ wavelengths NNS . SENT Secondly RB , , use NN of IN the DT CCP NP 4 CD program NN SCALEIT NP Collaborative JJ Computational JJ Project NN , , Number NP 4 CD , , 1994 CD option NN of IN isotropic JJ scaling NN versus CC diffraction NN resolution NN was VBD harnessed VVN . SENT This DT second JJ scaling NN step NN yielded VVD the DT best JJS quality NN dispersive JJ difference NN Patterson NP maps NNS in IN terms NNS of IN i NP a DT better JJR correspondence NN of IN the DT expected VVN Harker NP peaks NNS and CC ii NNS fewer JJR noise NN peaks NNS . SENT Fig NN . SENT 2 CD compares VVZ these DT difference NN Patterson NP maps NNS between IN the DT data NNS measured VVN at IN 1 CD . SENT 4889 CD and CC other JJ wavelengths NNS , , and CC with IN the DT calculated VVN f SYM dispersive JJ difference NN Patterson NP map NN . SENT Table NN 1 CD shows NNS the DT positions NNS , , in IN terms NNS of IN u NN , , v NN and CC w NN , , of IN the DT peaks NNS expected VVN from IN the DT known VVN crystal NN structure NN of IN NiSO NP 4 CD 6 CD H NN 2 CD O NN , , which WDT shows VVZ , , in IN particular JJ , , that IN the DT Ni NP Ni NP vectors NNS are VBP coincident JJ with IN the DT S NP S NP vectors VVZ . SENT However RB , , the DT Ni NP S NP cross NN vectors NNS should MD be VB much RB diminished VVN in IN the DT dispersive JJ difference NN Patterson NP . SENT thus RB the DT best RBS dispersive JJ Patterson NP map NN is VBZ the DT f NN dip NN 1 CD . SENT 8 CD , , i NP . SENT e SYM . SENT Fig NN . SENT 2 CD i NP . SENT Besides IN the DT 1 CD . SENT 8 CD reference NN wavelength NN set NN , , the DT other JJ candidate NN reference NN sets VVZ at IN 1 CD . SENT 3 CD and CC 2 CD . SENT 16 CD wavelengths NNS also RB show VVP good JJ Patterson NP sections NNS , , where WRB is VBZ the DT value NN of IN at IN one CD of IN the DT reference NN wavelengths NNS 1 CD . SENT 3 CD , , 1 CD . SENT 8 CD or CC 2 CD . SENT 16 CD , , but CC are VBP somewhat RB noisier JJR and CC have VHP less RBR diminished VVN cross NN vector NN peaks NNS . SENT The DT 1 CD . SENT 3 CD wavelength NN data NNS set VVN was VBD weak JJ in IN average JJ intensity NN owing VVG to TO the DT SRS NP bending VVG magnet NN c NN 4 CD . SENT The DT 2 CD . SENT 16 CD wavelength NN data NNS set VVN was VBD weak JJ owing VVG to TO increased JJ X NP ray NN absorption NN in IN the DT Be NP windows NNS and CC in IN the DT air NN path NN in IN the DT powder NN diffraction NN camera NN . SENT The DT dispersive JJ Patterson NP maps NNS for IN the DT non JJ CCP NP 4 CD scaled VVN data NNS in IN the DT supplementary JJ material NN show NN that IN the DT best JJS wavelength NN difference NN was VBD for IN the DT pair NN , , where WRB is VBZ the DT value NN of IN at IN the DT base NN of IN the DT Ni NP K NP absorption NN edge NN , , i NP . SENT e SYM . SENT compare VV Fig NN . SENT 2 CD iii NNS with IN Supplementary JJ Fig NN . SENT 2 CD iii NNS . SENT This DT is VBZ likely JJ to TO be VB the DT optimum JJ pair NN where WRB a DT further JJR scaling NN procedure NN is VBZ not RB needed VVN . SENT this DT could MD be VB a DT significant JJ point NN to TO guide VV which WDT immediate JJ analyses NNS to TO make VV at IN the DT beamline NN . SENT Figure NN 2 CD Comparison NN of IN dispersive JJ difference NN Patterson NP sections NNS w NN 0 CD , , w NN and CC w NN for IN i NP 1 CD . SENT 8 CD , , ii NP 1 CD . SENT 3 CD , , iii NP , , iv NP 2 CD . SENT 16 CD , , v NN calculated VVD 1 CD . SENT 8 CD . SENT The DT contour NN baseline NN was VBD based VVN on IN inspection NN of IN the DT maximum NN values VVZ away RB from IN the DT origin NN peak NN and CC from IN Harker NP sections NNS and CC thus RB was VBD an DT estimation NN of IN the DT noise NN level NN for IN each DT wavelength NN pair NN . SENT The DT contour NN interval NN was VBD 10 CD of IN the DT maximum JJ peak NN heights NNS in IN the DT Harker NP sections NNS for IN each DT wavelength NN pair NN . SENT Refinement NN of IN the DT structure NN was VBD carried VVN out IN using VVG SHELXL NP 97 CD Sheldrick NP , , 1997 CD and CC the DT starting VVG Ni NP atom NN position NN . SENT This DT showed VVD that IN the DT data NNS were VBD reasonably RB accurate JJ to TO 1 CD . SENT 5 CD resolution NN and CC also RB those DT data NN sets NNS that WDT were VBD collected VVN using VVG multiple JJ scans NNS were VBD the DT most RBS precise JJ . SENT In IN order NN to TO confirm VV that IN the DT values NNS obtained VVN from IN the DT data NNS for IN f NN were VBD reasonable JJ , , conventional JJ Rietveld NP refinements NNS were VBD performed VVN using VVG GSAS NP Larson NP Von NP Dreele NP , , 1994 CD . SENT The DT values NNS of IN f NN and CC f NN for IN Ni NP , , S NP and CC O NP atoms NNS were VBD initially RB set VVN at IN their PP$ theoretical JJ values NNS . SENT Then RB the DT positions NNS and CC temperature NN factors NNS of IN the DT atoms NNS were VBD allowed VVN to TO refine VV as IN was VBD the DT value NN of IN f NN for IN the DT Ni NP atom NN . SENT Table NN 2 CD shows NNS the DT refined VVN and CC calculated VVN values NNS of IN f NN for IN the DT Ni NP atom NN at IN the DT various JJ wavelengths NNS , , showing VVG that IN the DT refined JJ values NNS for IN f NN agree VVP reasonably RB closely RB with IN the DT expected VVN values NNS . SENT Table NN 2 CD Values NNS of IN f NN at IN the DT various JJ wavelengths NNS The DT refined JJ values NNS were VBD obtained VVN using VVG GSAS NP . SENT the DT value NN at IN 2 CD . SENT 1608 CD used JJ data NNS truncated VVN at IN 1 CD . SENT 506 CD resolution NN . SENT The DT calculated JJ values NNS are VBP from IN Sasaki NP 1989 CD . SENT f SYM refined JJ e NN f SYM calc NP . SENT e SYM 1 CD . SENT 4889 CD 7 CD . SENT 361 CD 12 CD . SENT 025 CD 1 CD . SENT 4912 CD 6 CD . SENT 565 CD 6 CD . SENT 272 CD 1 CD . SENT 7962 CD 2 CD . SENT 253 CD 1 CD . SENT 597 CD 1 CD . SENT 3002 CD 1 CD . SENT 319 CD 1 CD . SENT 071 CD 2 CD . SENT 1608 CD 0 CD . SENT 064 CD 1 CD . SENT 074 RB The DT anomalous JJ scattering NN tables NNS Sasaki NP , , 1989 CD show NN that IN the DT calculated JJ minimum NN is VBZ at IN a DT wavelength NN of IN 1 CD . SENT 4878 CD for IN a DT sampling VVG interval NN of IN the DT calculation NN used VVN of IN 0 CD . SENT 0001 CD . SENT Our PP$ value NN quoted VVN here RB of IN 1 CD . SENT 4889 CD is VBZ , , as RB explained VVD earlier RBR in IN the DT text NN , , subject JJ to TO a DT calibration NN offset VVN but CC is VBZ the DT f NN dip NN position NN in IN fact NN . SENT A DT wavelength NN shift NN of IN 0 CD . SENT 0023 CD from IN 1 CD . SENT 4889 CD to TO 1 CD . SENT 4912 CD allows VVZ simple JJ interpolation NN to TO the DT second JJ calculated JJ value NN tabled VVD here RB of IN 6 CD . SENT 272 CD e NN from IN 12 CD . SENT 025 CD e NN . SENT The DT refined JJ value NN of IN 7 CD . SENT 361 CD e NN is VBZ not RB as RB negative JJ as IN we PP would MD anticipate VV owing VVG presumably RB to TO smearing VVG factors NNS of IN the DT instrument NN and CC limitations NNS of IN the DT Rietveld NP approach NN . SENT A DT particular JJ interest NN is VBZ the DT experience NN with IN the DT longest JJS wavelength NN data NNS set VVD recorded VVN , , i NP . SENT e SYM . SENT at IN 2 CD . SENT 16 CD wavelength NN . SENT We PP refined VVN against IN the DT 2 CD . SENT 16 CD data NNS . SENT The DT data NNS set NN has VHZ the DT worst JJS data NN statistics NNS , , with IN wRp NP 0 CD . SENT 250 CD , , Rp NP 0 CD . SENT 192 CD . SENT This DT is VBZ reflected VVN in IN the DT refined JJ values NNS of IN f NN obtained VVN when WRB using VVG all PDT the DT data NN range NN , , which WDT was VBD 4 CD . SENT 591 CD e NN . SENT this DT is VBZ greater JJR than IN that DT at IN 1 CD . SENT 8 CD wavelength NN . SENT The DT other JJ problematic JJ feature NN was VBD that IN , , whereas IN in IN all PDT the DT other JJ data NN sets NNS Uiso NP was VBD positive JJ for IN all DT atoms NNS , , this DT was VBD not RB the DT case NN for IN the DT Ni NP atom NN here RB where WRB the DT Uiso NP became VVD negative JJ . SENT These DT problems NNS can MD be VB traced VVN to TO the DT data NNS collection NN being VBG based VVN simply RB on IN repeat NN scans NNS . SENT So RB whilst IN the DT signal NN to TO noise NN at IN low JJ angles NNS is VBZ good JJ , , the DT reflections NNS at IN high JJ angle NN are VBP worse JJR . SENT However RB , , a DT further JJR refinement NN was VBD carried VVN out IN using VVG the DT 2 CD . SENT 16 CD wavelength NN data NNS set VVN but CC truncating VVG the DT data NNS at IN a DT resolution NN of IN 1 CD . SENT 506 CD . SENT This DT refinement NN led VVD to TO a DT refined JJ f NN value NN of IN 0 CD . SENT 064 CD e NN , , which WDT is VBZ much RB closer JJR to TO the DT theoretical JJ value NN of IN 1 CD . SENT 074 CD e NN . SENT in IN addition NN , , all PDT the DT isotropic JJ temperature NN factors NNS remained VVD positive JJ . SENT 5 LS . SENT Discussion NN and CC conclusions NNS The DT choice NN of IN Ni NP SO IN 4 CD 6 CD H NN 2 CD O NN had VHD , , as RB well RB as IN the DT benefits NNS listed VVN above IN , , the DT complication NN that IN its PP$ space NN group NN was VBD P NN 41212 CD , , which WDT in IN an DT unknown JJ case NN could MD have VH been VBN P NN 43212 CD , , i NP . SENT e SYM . SENT the DT enantiomeric NN space NN group NN . SENT To TO resolve VV such PDT a DT choice NN with IN PDD NP would MD require VV supplementary JJ information NN such JJ as IN prior JJ chemical NN knowledge NN of IN the DT hand NN . SENT In IN the DT protein NN case NN , , the DT enantiopurity NN is VBZ known VVN because IN all DT naturally RB occurring VVG proteins NNS are VBP comprised VVN of IN left JJ handed VVN amino NN acids NNS . SENT There EX is VBZ then RB a DT potential JJ limitation NN of IN PDD NP where WRB the DT prior JJ chemical NN knowledge NN is VBZ not RB available JJ . SENT The DT additional JJ SCALEIT NP data NNS scaling NN used VVD here RB proved VVN to TO be VB helpful JJ to TO the DT quality NN of IN the DT PDD NP Patterson NP maps NNS . SENT There EX are VBP quite RB a DT few JJ options NNS that WDT can MD be VB applied VVN to TO optimize VV the DT signal NN extraction NN between IN the DT data NN sets VVZ at IN different JJ wavelengths NNS . SENT we PP have VHP explored VVN one CD in IN detail NN here RB and CC it PP was VBD successful JJ . SENT It PP was VBD particularly RB interesting JJ that IN the DT pair NN , , with IN its PP$ very RB small JJ wavelength NN shift NN , , gave VVD good JJ results NNS without IN this DT additional JJ data NNS set VVN to TO data NNS set VVN scaling NN . SENT Scaling NN , , however RB , , might MD not RB work VV and CC this DT potential JJ limitation NN needs VVZ to TO be VB explored VVN in IN more JJR detail NN and CC suitable JJ protocols NNS developedOur NN way NN of IN estimating VVG the DT f NN values NNS gave VVD quantitatively RB sensible JJ results NNS . SENT Another DT way NN that WDT is VBZ used VVN is VBZ the DT Kramers NP Kronig NP transform VV KKT NP Evans NP Pettifer NP , , 1999 CD . SENT We PP have VHP explored VVN the DT softer JJR X NP ray NN range NN here RB but CC of IN course NN we PP must MD mention VV its PP$ possible JJ limitations NNS . SENT In IN particular JJ , , the DT increased JJ absorption NN on IN the DT instrument NN , , e NN . SENT g NN . SENT air NN paths NNS , , and CC in IN the DT sample NN , , in IN effect NN , , can MD reduce VV the DT signal NN and CC thereby RB the DT signal NN to TO noise NN ratio NN of IN the DT data NNS , , clearly RB not RB wished VVN for IN . SENT However RB , , the DT core NN idea NN is VBZ that IN , , for IN larger JJR unit NN cells NNS , , the DT powder NN lines NNS can MD be VB spread VVN out RP by IN using VVG softer JJR X NN rays NNS . SENT Of IN course NN , , this DT requires VVZ implicitly RB that IN the DT peaks NNS individually RB do VVP not RB widen VV more RBR than IN the DT gain NN in IN their PP$ increased JJ angular JJ separation NN . SENT This DT depends VVZ on IN the DT instrument NN and CC the DT sample NN of IN course NN but CC is VBZ generally RB true JJ . SENT A DT tunable JJ undulator NN based VVN instrument NN , , with IN its PP$ tiny JJ divergence NN , , has VHZ an DT ideal JJ specification NN for IN exploring VVG the DT relative JJ gains NNS and CC losses NNS in IN the DT various JJ wavelength NN range NN regimes NNS of IN interest NN . SENT Very RB recently RB , , Cernik NP et CC al NP . SENT 2005 CD have VHP published VVN details NNS of IN powder NN diffraction NN pattern NN recording NN at IN a DT wavelength NN as RB long RB as IN 5 CD on IN an DT SRS NP bending VVG magnet NN , , and CC so RB longer JJR wavelength NN experience NN is VBZ growing VVG . SENT Overall RB , , we PP have VHP shown VVN the DT following NN . SENT i NP The DT two CD wavelength NN difference NN Patterson NP maps NNS based VVN on IN coefficients NNS FLH NP 2 CD FLH NP 1 CD 2 CD even RB where WRB there EX is VBZ one CD Ni NP atom NN in IN the DT presence NN of IN a DT few JJ light JJ atoms NNS for IN our PP$ test NN case NN yielded VVD vectors NNS dominated VVN by IN the DT anomalous JJ scatterer NN alone RB . SENT ii NP The NP Ni NP atom NN position NN determined VVN in IN i NP allowed VVD difference NN Fourier NP cycling NN development NN of IN the DT rest NN of IN the DT structure NN from IN the DT anomalous JJ scatterer NN position NN using VVG single JJ wavelength NN data NNS . SENT iii NP The DT use NN of IN 1 CD . SENT 5 CD resolution NN proved VVN to TO be VB adequate JJ for IN i NP and CC ii NP . SENT iv NN The DT softer JJR X NP ray NN wavelength NN data NNS set VVD quality NN assessment NN had VHD several JJ problems NNS with IN it PP . SENT of IN especial JJ note NN is VBZ the DT incorrect JJ refined JJ f NN value NN . SENT Improvements NNS in IN data NN collection NN by IN using VVG a DT helium NN path NN as RB well RB as IN our PP$ repeat NN scans VVZ strategy NN is VBZ believed VVN to TO be VB needed VVN because IN of IN the DT already RB weak JJ high JJ angle NN data NNS being VBG absorbed VVN by IN air NN to TO make VV them PP too RB weak JJ . SENT The DT low JJ angle NN reflections NNS suffered VVD the DT same JJ fate NN but CC were VBD strong JJ enough RB to TO give VV a DT reasonable JJ signal NN to TO noise NN ratio NN . SENT Pursuing VVG this DT category NN of IN powder NN diffraction NN data NN collection NN we PP believe VVP is VBZ important JJ because IN it PP is VBZ a DT simple JJ strategy NN to TO spread VV out RP the DT powder NN lines NNS and CC it PP widens VVZ the DT f NN range NN of IN values NNS that WDT can MD be VB stimulated VVN for IN a DT variety NN of IN important JJ elements NNS like IN the DT transition NN metals NNS in IN inorganic JJ chemistry NN structural JJ studies NNS , , halogens NNS in IN pharmaceutical JJ industry NN new JJ drug NN discovery NN studies NNS and CC sulfur NN , , selenium NN , , xenon NN or CC iodine NN in IN future JJ protein NN crystallography NN powder NN analyses NNS . SENT Overall RB , , in IN our PP$ future JJ synchrotron NN powder NN f SYM PDD JJ experiments NNS , , we PP will MD explore VV extension NN to TO larger JJR organic JJ and CC inorganic JJ structures NNS than IN our PP$ test NN case NN where WRB we PP believe VVP that IN , , in IN cases NNS of IN a DT single JJ anomalously RB scattering VVG atom NN in IN the DT asymmetric JJ unit NN of IN a DT crystal NN , , the DT scope NN of IN ab NP initio NP structure NN solution NN from IN powder NN diffraction NN data NNS can MD be VB considerably RB extended VVN with IN our PP$ approach NN . SENT Moreover RB , , our PP$ PDD JJ approach NN can MD be VB extended VVN to TO proteins NNS containing VVG metal NN atoms NNS , , selenomethionine NN or CC perhaps RB even RB sulfur NN , , and CC where WRB one CD data NNS set VVN of IN the DT PDD JJ group NN of IN data NN sets NNS per IN study NN can MD harness VV the DT benefits NNS of IN softer JJR X NP rays NNS referred VVD to TO above RB , , i NP . SENT e SYM . SENT especially RB spreading VVG out RP the DT pattern NN but CC also RB increasing VVG the DT sample NN scattering NN efficiency NN , , which WDT varies VVZ as IN 2 CD . SENT Especially RB exciting JJ would MD be VB extending VVG to TO yet RB smaller JJR protein NN crystal NN samples NNS , , which WDT would MD otherwise RB be VB outside IN the DT range NN of IN X NP ray NN data NN collection NN from IN a DT protein NN microcrystal NN . SENT In IN effect NN , , in IN the DT protein NN powder NN case NN the DT sample NN volume NN is VBZ not RB restricted VVN , , unlike IN the DT protein NN single JJ microcrystal JJ case NN , , offering VVG a DT strategy NN for IN getting VVG around RP sample NN X NN radiation NN damage NN . SENT The DT various JJ experimental JJ avenues NNS and CC optimizations NNS are VBP quite RB numerous JJ and CC will MD be VB investigated VVN systematically RB . SENT AcknowledgementsWe NNS are VBP grateful JJ to TO C NP . SENT C SYM . SENT Tang NP of IN SRS NP Daresbury NP for IN helpful JJ advice NN on IN using VVG SRS NP station NN 2 CD . SENT 3 LS . SENT References NNS Burger NP , , K NP . SENT , , Cox NP , , D NP . SENT , , Papoular NP , , R NP . SENT Prandl NP , , W NP . SENT 1998 CD . SENT J NP . SENT Appl NP . SENT Cryst NP . SENT 31 CD , , 789 CD 797 CD . SENT Cernik NP , , R NP . SENT J NP . SENT . SENT Cheetham NP , , A NP . SENT K NN . SENT , , Prout NP , , C NP . SENT K NP , , Watkin NP , , D NP . SENT J NN . SENT , , Wilkinson NP , , A NP . SENT P NN . SENT Willis NP , , B NP . SENT T NN . SENT M NP . SENT 1991 CD . SENT J NP . SENT Appl NP . SENT Cryst NP . SENT 24 CD , , 222 CD 226 CD . SENT Cernik NP , , R NP . SENT J NN . SENT , , Husheer NP , , S NP . SENT , , Smith NP , , A NP . SENT Roper NP , , M NP . SENT 2005 CD . SENT J NP . SENT Synchrotron NN Rad NP . SENT 12 CD , , 431 CD 433 CD . SENT Collaborative JJ Computational JJ Project NN , , Number NP 4 CD 1994 CD . SENT Acta NP Cryst NP . 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SENT , , Stephens NP , , P NN . SENT W NN . SENT , , Smith NP , , G NP . SENT D SYM . SENT Blessing NN , , R NP . SENT H NP . SENT 2000 CD . SENT Acta NP Cryst NP . SENT D NP 56 CD , , 1549 CD 1553 CD . SENT Wood NN , , I PP . SENT G NN . SENT , , Nicholls NP , , L NP . SENT Brown NP , , G NP . SENT 1986 CD . SENT J NP . SENT Appl NP . SENT Cryst NP . SENT 19 CD , , 364 CD 371 CD . SENT Acta NP Cryst NP 2005 CD . SENT A DT 61 CD , , 568 CD 574 CD doi NP . SENT 10 CD . SENT 1107 CD S NP 010876730503237 CD X NP