圓二色譜circulappt課件-資料下載頁
2025-05-06 23:20本頁面
【正文】 ble. Sample concentration and cell pathlength ?A good suggestion is to run in advance an absorption UVVIS spectra. ?CD spectroscopy calls for same requirements as UVVIS: best S/N is obtained with absorbance level in the range to . It’s usually difficult to get proper data when absorbance (of sample + solvent) is over 2 . Typical Conditions for protein CD ? Protein Concentration: mg/ml ? Cell Path Length: 1 mm ? Volume 350 ml ? Need very little sample mg ? Concentration reasonable ? Stabilizers (Metal ions, etc.): minimum ? Buffer Concentration : 5 mM or as low as possible while maintaining protein stability 溶劑的吸收 !!! Buffer Systems for CD Analyses ?Acceptable: 1. Potassium Phosphate with KF, K2SO4 or (NH4)2SO4 as the salt. 2. Hepes, 2mM. 3. Ammonium acetate, 10mM. ?Avoid: Tris。 NaCl。 Anything optical active, . Glutamate Summary ? CD is a useful method for looking at secondary structures of proteins and peptides. ? CD is based on measuring a very small difference between two large signals must be done carefully ? the Abs must be reasonable max between ~ and ~. ? Quarts cells path lengths between cm and 10 cm. 1cm and cm mon ? have to be careful with buffers TRIS bad high UV abs ? Measure cell base line with solvent ? Then sample with same cell inserted same way around ? Turbidity kills filter solutions ? Everything has to be clean ? For accurate 2ndry structure estimation must know concentration of sample 核酸的 CD信息 BZ? Or ZB？ 建議濃度：在吸光值 510倍 圓二色譜在糖類化合物結(jié)構(gòu)分析中的應(yīng)用 ? 碳水化合物的結(jié)構(gòu)決定 CD的強(qiáng)度和形狀，而從 CD獲得的構(gòu)象信息的多少取決于樣品結(jié)構(gòu)的復(fù)雜程度； ? 對(duì)那些具有較好重復(fù)系列的糖類化合物而言， CD能提供更為可靠的空間結(jié)構(gòu)信息。 ? 對(duì)那些結(jié)構(gòu)比較復(fù)雜的糖類來說，即使不能直接測(cè)定糖類化合物的絕對(duì)構(gòu)象，利用一些經(jīng)驗(yàn)規(guī)則，例如，CD可以用來推斷糖類是否具有 gt構(gòu)象，而且 CD可以作為探針來測(cè)定糖類化合物構(gòu)象的變化，如膠體 溶液或無序 有序的轉(zhuǎn)變過程。 THANKS!
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