Amino acids raman spectra

First, it is possible to excite a chromophore corresponding to the active site, and detennine which modes interact with it. Second, by using UV excitation, the amino acids with phenyl rings (tryptophan and tyrosine, and a small contribution from phenylalanine) can be selectively excited [4], The frequency shifts in the resonance Raman spectrum associated with them provide infomiation on their enviromnent. 

In Eq. (10), E nt s(u) and Es(in) are the s=x,y,z components of the internal electric field and the field in the dielectric, respectively, and p u is the Boltzmann density matrix for the set of initial states m. The parameter tmn is a measure of the line-width. While small molecules, N<pure solid show well-defined lattice-vibrational spectra, arising from intermolecular vibrations in the crystal, overlap among the vastly larger number of normal modes for large, polymeric systems, produces broad bands, even in the crystalline state. When the polymeric molecule experiences the molecular interactions operative in aqueous solution, a second feature further broadens the vibrational bands, since the line-width parameters, xmn, Eq. (10), reflect the increased molecular collisional effects in solution, as compared to those in the solid. These general considerations are borne out by experiment. The low-frequency Raman spectrum of the amino acid cystine (94) shows a line at 8.7 cm- -, in the crystalline solid, with a half-width of several cm-- -. In contrast, a careful study of the low frequency Raman spectra of lysozyme (92) shows a broad band (half-width 10 cm- -) at 25 cm- -,... 

The new NIR FT Raman spectroscopy now allows the investigation of food (Keller et al., 1993). Fig. 4.1.20 shows typical Raman spectra of food components carbohydrates, proteins, and lipids. Fig. 4.1-20C shows the Raman spectrum of a banana with the out-of-phase and in-phase vibrations of the C-O-C groups of the carbohydrates at about 1100 and 850 cm. Fig. 4.1-20B, a Raman spectrum of turkey breast shows the amide I and III bands and some bands which can be directly assigned to amino acids. The Raman spectra of lipids allow the determination of the amount of cis and trans disubstituted C=C bonds Fig. 4.1-20A, butter (Keller et al., 1993). NIR Raman spectroscopy has good chances as tool for the investigation of living tissues, especially in medical diagnostics (Keller et al., 1994 Schrader et al., 1995). 

Figure 8.47. Raman spectrum of native form ai- add g tx)pcoteiiL (Bottom) Raman difference spectrum of native tti- acid glycoprotein minus ai acid glycoprotein wMi tiound progesterone. Positions of amino acids with aromatic side chains, wiA respect to their environment or surface of the protein, have been also determined. Cuitosey from Vbdimir Kopecky Jr., ROd er Enrich, Katefina Hofbauoova and Vladimir Baumnic...

Figure 5 presents a UV Raman spectrum of BR excited at 240 nm. The spectra are of excellent quality and reveal unique enhancement of the vibrations of just the tyrosine and tryptophan residues. With UV excitation, the aromatic amino acids experience resonance enhancement, and we can selectively examine their vibrational structure. Experiments of this type have been used to determine the protonation state of key... 

Recently the SERS spectra of on silver hydrosols adsorbed aromatic amino acids have also been studied The Raman spectra are enhanced from 1(K) to 2(K) times in the presence of silver colloids with primary sol particles 14 nm in size. The hydrosol-Phe interaction shows the strongest SERS spectrum. The frequency shifts between the NSRS- and SERS spectra are small (1-15 cm" ). The following SERS bands are characteristic for the aromatic amino acids Phe, 1005, 1034 and 1049cm" Trp, 762,1340 and 1377 cm - Tyr, 831,988,1169 and 1299 cm - His, 670 and 1310 cm -. ... 

The following amino acids have been definitely excluded as part of a common structure of the Type 1 center Tryptophan has been eliminated as a ligand for the reasons given in Section IIAl. Arginine is absent in the plastocyanins. Tyrosine has been eliminated by optical absorption studies of azurin and by a recent analysis of the resonance enhanced Raman spectrum of stellacyanin 206). 

Further applications of n.m.r. techniques in specific enzyme systems are discussed below. E.p.r. has been used to investigate the bonding of copper(ii) in several amino-acid, peptide, and trypsin complexes, and the effects of divalent metal ions on the Raman spectrum of ATP in aqueous solution have also been reported. ... 

We have demonstrated that Ag nanorod-based SERS is not only sensitive to purified virus, but also is able to sense the presence of virus after infection in biological media 49). To demonstrate this, we compared the SERS spectra of uninfected Vero cell lysate, RSV-infected cell lysate and purified RSV. The results show that major Raman bands can be assigned to different constituents of the cell lysate and the virus, such as nucleic acids, proteins, protein secondary structure units and amino acid residues present in the side chains and the backbone. However, our most significant result was that vibrational modes due to the virus could be unambiguously identified in the SERS spectrum of the Vero cell lysate after infection 49). 

They have carried out similar kind of study with BSA also. They have noticed the formation of AU25 along with the Aug intermediate and concluded that the core might be the same but the growth depends completely on the nature of the protein. The above mentioned proteins are bigger (583 amino acid residues) and so it is expected that they can accommodate smaller 1 nm cluster core within. But when the protein size is smaller like insulin, there is a chance that clusters cannot form inside the protein rather multiple proteins can stabilize one core. Such type of studies were done with insulin where clusters were grown uniformly inside micro-crystals of protein and that was proved by depth dependent two-photon excitation spectroscopy and RAMAN spectroscopy but mass spectrum is not available for this specific system. ... 

The vibrational spectra of reference material are introduced in Figure 3.1, which belong to the main components of soft tissue. The IR spectrum (trace A) and Raman spectrum (F) of the all-beta protein concanavalin A are shown in Figure 3.1. IR bands due to the peptide backbone with P-sheet secondary structures are found at 3284 (amide A), 1636 (amide I), 1531 (amide II), and 1235 cm-i (amide III). Bands at 1403 (COO ) and 2963, 2874, 1455 cm- (CHg) are assigned to amino acid side chains. These bands are located in the Raman spectrum at similar positions at 1398 and 1449 cm . The Raman amide I band is centered at 1672 cm , the amide III band at 1238 cm , and the weak amide II band is not observed. Instead, other Raman bands of amino acids are identified at 759 and 1555 cm for Trp 621,1003, 1031, and 1208 cm for Phe 643, 829, and 853 cm for Tyr and 1126, 1317, and 1340 cm (CH2/CH3) for aliphatic amino acids. The IR spectrum (B) and Raman spectrum (G) of the all alpha protein bovine serum albumin show a number of differences. The amide bands... 

The data are typical for other amino-acid amides. The peak at 3370 cm- in the NH-stretching region of the compound studied corresponds to the indole VMH(r) stretching mode and the 3268 cm peak to a combination mode. All the obtained characteristic peaks for indole ring correlated well with the known ones for the pure amino acid tryptophan, and with theoretical vibrational analysis and IR spectroscopic data of some homo- and heterodipeptides with tryptophyl-fragments. The Raman spectrum of L-tryptophanamide esteramide ester amide of squaric acid diethyl ester is depicted in Figure 4.34. 

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