碩士生物儀器分析之紫外-可見光譜-資料下載頁
2025-01-16 20:33本頁面
【正文】 Vis光譜圖 The n electrons (or the nonbonding electrons) are the ones located on the oxygen of the carbonyl group of tetraphenyclopentadienone. Thus, the n to pi* transition corresponds to the excitation of an electron from one of the unshared pair to the pi* orbital. Tetraphenylcyclopentadienone 四苯基環(huán)戊二烯酮 Protein absorbances e from 3 sources 1. Peptide Bond Asp, Glu, Asn, Gln, Arg, and His sidechains have absorption in this region also (190 230 nm) but is very weak pared to peptide bond p p*. Absorption in the 190230 nm region can be and is used to quantitate protein/peptide concentrations, but this is plicated by many pounds used in buffers which also absorb at these wavelengths. What about Proteins? What about Proteins? Phe ?250 = 400 symmetry forbidden p p* Tyr ?274 = 1400 p p* Trp ?280 = 4500 at least 3 different transitions. A280 is one of the most monly used methods to measure protein concentration (aside from colorimetric methods such as the Lowry or Bradford dye binding assays), but this method is obviously very sensitive to differences in amino acid position. 2. Aromatic Amino Acids most useful Protein absorbances e from 3 sources What about Proteins? Protein absorbances e from 3 sources 3. These transitions can change with pH。 especially Tyr Others: Prosthetic Groups Nucleotides . FMN, NAD Heme Cu Retinal etc.. ? Nucleotide spectra are plicated to analyze quantitatively because there are many nonbonded electrons. Expect several different p p* and n p* transitions at each region between 200 nm and 300 nm. ? All nucleotides have lmax near 260 nm which is not affected by sugar phos. configuration == can measure nucleic acids at 260 nm to estimate concentration. ?260 = ~ 1 x 104 M1 === very sensitive and can measure concentrations down to approx. 3 181。g/ml. What about Nucleic Acids? UVVis can gives us information about the electronic energy levels of a pound
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