多探针功能DRCD测定丙氨酸粉末

虽然CD样品通常必须在溶液或透明薄膜中才能进行CD测量，但最近对不溶性样品或溶液中构象改变的样品的CD测量的需求越来越大。这些样品必须在固态下进行，虽然CD传输测量可以对固体样品进行，但制备需要将样品制成颗粒形式。此外，如果需要样品稀释，则不容易回收样品。克服固体下传输测量困难的一种方法是使用漫反射CD（DRCD）。漫射反射是在不同方向散射的入射光。在DRCD中，光谱仪光束聚焦于粉状样品，通过使用积分球，收集了漫反射光（图1A）。这使得DRCD成为一种很好的固体样品技术。然而，在固体样品的CD测量中，可能必须考虑由固体样品光学各向异性产生的LD（线性二色性）的影响，以减少CD谱中的任何伪影。J-1500 CD光谱仪允许用户同时使用多探针数字四通道锁相放大器对CD和LD进行测量。对CD和任何伪影的测量都可以不进行第二次测量。结论：该应用证实了DRCD-575粉末CD单元和具有多探针功能的J-1500分光偏振仪可以用于良好粉末氨基酸样品的DRCD测量。该测量技术可以很容易地扩展固态CD在金属配合物和超分子样品中的应用。Application Note Measurement of alanine powder using DRCDwith multiprobe function2/3Application Note CDS Spect r oscop y Measurement of alanine powder using DRCDwit h multiprobe function Wh il e C D sam p l es m u s t t ypi c all y be in s ol u ti o n or a transpa ren t fi lm in o r d er to p e r f o rm C D m e as u remen t s ，there has r ecently been an i ncreasing d e mand f or CD m e as uremen ts o n in so l u bl e sa mpl es o r sam ple s th a t ch a n ge con fo r m ati o n in so lu ti o n . Th e se sampl e s m ust b e p e r fo rm ed in a solid state and w h ile CD trans m i ss i on m eas u remen t s c an b e m ad e o n sol i d sa mpl es， t h e pr epar ati o n r e q uire s th e s ampl e t o b e made in t o a p e l let f o rm. In additi o n ， if s a mple d il u t io n i s requ ir ed ， i t i s n o t easy to r ecove r the sa mpl e. A way of ove r c om i ng th e d i f f i cul t i e s of tran s miss i o n me a s ur e men ts in the s o l i d st a te i s to u s e d iffu s e-re fl e ct a n c e CD (D R CD). Di ffu se reflectance i s i n ciden t l i gh t th a t is scat t e r ed off a s u r f ace in d i f f eren t d ir ecti o n s. I n D RCD， the s pe c trom eter b ea m f oc u ses o n the pow d e re d sample and th ro u gh the u s e of a n in te g rating sp h ere， the dif f u s e l y r ef l ected li gh t is co ll ecte d (F ig u r e 1A ). Th i s m a k e s D RCD a n exc e l l e n t te chn iq u e for solid s a m pl es . H o wever， duri n g CD m easuremen t s o f solid sa m ples， th e i n fluence of L D (l in e ar d i c hroi sm ) d e r i v ed f ro m t h e o pt ica l a ni s ot ro py of the sol i d sample may h a v e t o b e taken into cons i d e r a t ion to mi n imize a ny ar t ifa c ts in th e CD spect ru m. T h e J-1500CD sp ectro m eter all ow s the u s e r t o ma k e a simu lt a n eo u s m ea s uremen t u sing a mu lti -pro b e d i gital q ua d lo c k -in am p li f ier f or bo th CD and LD. The meas ur eme n t o f t h e CD an d a ny art i fac t s ca n b e m a de w i th ou t a s eco n d m ea s uremen t. T h is app li cation note illu s trate s the DRC D meas u re m e n t u sing th e DRCD-575 accessory (F i gure 1B) and the J-1500CD sp ectr om e t er w i th m u lti -pr obe f u n cti o n al i ty. Th is is demo n s tr ated by a n example DRC D meas u r eme n t u s ing p owdered L- a nd D-a lanin e . Keywords J -1500， c ir c u l a r d i c h r o i s m ， l i n e ar d ichro i s m ， di ff us e -re flec t an ce C D ， D R C D -575， so l i d st a t e， mu lti-p ro b e ，bi ochemist r y 28600 Mary's Court ， Ea s t on， MD 21601 U S A Experimental Fi g u re 1A sh o w s that the d i ff u se r ef l ectan c e can b e me as u re d b y p l a c i ng a po w d er ed samp l e o ppo s i te th e i n l e t p o r t of the inc i de n t l ig h t and placin g t h e de t ector in c l ose c o n t act w i t h the i nteg r a tin g sph e re (90° to t h e a xis of th e i n ciden t l ig h t ). A d iffus e-tran s miss i o n mea s u r e m en t can be made wh e n a sa mpl e is set a t th e i n l et p o r t o f the i n ci d e n t li g h t a n d a d i ff u s e plate o r w h it e pl a t e is l oc a t ed a t th e s a mple p o s i ti o n t o c ol l e c t the d i ff u se re f l ect a n c e. I n d iff u se trans m i s s i o n ，sample di lu tion is ofte n re q uires and small samp l e am o un ts ca n be m easured . Figure 3. (A) Optical layout of the DRCD-575 accessory and t he (B) DRCD-575 Powder CD unit. System configuration Model Description P/N Main unit J-1500-450ST CD spectrometer' 7000-J006A Accessory PLM-534 FDCD PMT detector 7069-J034A FLM-525 N2 gas flow meter 7069-J025A DRCD-575 Solid-state (powder) CD measurement unit23 7069-J075A Thi s app li cation ca n al so be perfor m ed u s i n g th e J-1500-150S T (P /N 7000-J005A ). P owd e r C D u nit ca n be app li ed to t he tr a n s m i s s i on meas u r e me nt us in g KBr pel l et m e th od. T h e c el l ho l de r for p o wde r ed sa m ple i s a s t and a r d i t e m i n t h e DRCD -575ac ce s s or y. Measurement conditions Data acquisition interval 0.1nm Response time 1 sec Spectral bandwidth 2nm Scan speed 100nm/min Accumulations 5 times Results The DRC D and DRLD spe c t r a of L - a n d D-alanin e powde r ed samp l es a r e shown i n F i gu r e 2. In the CD mod e ， the L -a n d D-a l an i ne spectra ob t a i ned are m i rro r i mag es of o n e a nother wi th th e s a me in ten si t y . I n the LD mod e， the s i gnal in te n si t y o f ea c h s p ectru m is less th a n ± 0.005 A O D ， wh i c h i s sm a ll en o u gh to n ot co n tribu t e sig ni fi c an tly. These resul t s i n dicate th at t he in f luence due to opti c al a n iso t r opy i s ne g ligi bl e. Figure 2. CD (top) and LD (bottom) spectra for L-alanine (blue) and D-alanine (red). Conclusion T h i s appli ca ti o n co n fi r m s that th e DRCD-575 Powd e r CD un it a nd th e J -1500 sp e ctro p o l ar i meter wi t h mu lti -p r o b e f u nc ti o n ca n b e u sed fo r D R C D me as ure m en t s of w ell-g r o u nd p o wder a mino ac id s a mp l es . Thi s m eas u re m en t t echn iqu e co u ld easily e x p a n d the app li catio n of solid-s t a t e CD to meta l co m plexes a n d su p er mo l ec u le samp l es. References 1. E. Cast i g l ion i a nd P. A lb e r tini ， Ch ir a lit y (2000)，12，291-294 2. Qi u ， H .， In o u e，Y .， an d S . Che ， A n gew. C h em . In t. E d (2009)， 48，3069-3072. 28600 Mary's Cour t ， E asto n ， MD 21601US A