Spectra valine

The DQFCOSY spectrum of RpII in D O is shown in Figure 2. Each cross peak in this spectrum identifies a pair of coupled spins of the amino acid side chains. Since couplings are not propagated efficiently across amide bonds, all groups of coupled spins occur within individual amino acids. The chemical structure of an amino acid side chain is reflected in the characteristic coupling network and chemical shifts (13). Valine spin system (CH-CH-(CH3)2) explicitly shown in Figure 2 as an example. 

Figure 2. DQFCOSY spectrum of RpII in D2O. Cross peaks corresponding to a-P protons of various spin systems are labeled. The valine spin systems are shown explicitly.

It was straightforward to identify the spin systems of four valines, five threonines, four alanines, three glycines, two glutamates, and AMX type residues (Asp, Cys, Phe, Tyr, Trp, and Ser) of this protein from the COSY, RELAY, and NOESY spectra in D O solution. The RELAY spectrum was particularly useful in identification of Val, Ala, Thr, and Glu spin systems. 

TAG-CH3 and TAG-CH2-, acyl chain terminal-CH3 and bulk (-CH2-)n groups, respectively, of fatty acids (predominantly triacylglycerols) associated with chylomicron- and very low-density lipoprotein (VLDL) Thr, threonine-CHs Val, valine-CHs. The asterisk In spectrum (b) denotes a radiolytically-generated 2.74 p.p.m. 

Figure 10.11 MS/MS spectra of a tryptic piece of the 11,222 Da protein (top spectrum) and the 11,236 Da protein (bottom spectrum). Both proteins were identified as homologous to a conserved hypothetical protein of Salmonella enterica serovar Typhi. The only difference observed in the sequence is that of a substitution of valine with leucine, which increases the molecular weight of the protein by 14 Da.

The H- and C-NMR spectroscopic data support the proposed primary structure of poly(Lys-25). The amide carbonyl resonances are particularly informative as these signals are well resolved in the C-NMR spectrum of poly(Lys-25) (Figure 4). An amide carbonyl resonance is observed at 174.9 ppm for poly(Lys-25) that does not appear in the spectrum of poly(Val-Pro-Gly-Val-Gly) [13]. The position and relative intensity of this resonance are consistent with a lysine amide carbonyl group within a peptide bond [14]. Moreover, the resonances of the amide carbonyl groups for other residues in the pentapeptide repeat are split due to the substitution of a lysine residue at position 4 in every fifth pentapeptide in Lys-25. In addition, the absence of splitting in amide carbonyl group of valine in position 4 (174.5 ppm) supports this assignment, as this residue is replaced by lysine in the fifth pentapeptide of the Lys-25 repeat. The presence of other resonances attributable to the lysine residue can be detected in the H- and C-NMR spectra of the Lys-25 polymer at levels commensurate with its... 

Study the H spectrum of valine in Figure 5.14A and match each peak to the corresponding proton in the chemical structure. Explain any spin-spin coupling. 

Study the 13C spectrum of valine in Figure 5.14A. Identify the carbon atom that produces each peak in the spectrum. 

Fig. 3.36 Infrared spectrum of ( )-valine recorded as a Nujol mull.

The results are summarized in Fig. 65,36 The position of labeling of the cephalosporin follows directly from the position, in the 13C spectrum, of the peak enhanced by labeling when the precursor is stereospecifically methyl-13C labeled valine. The position of labeling of the penicillin, a or p, was deduced on the basis of an earlier assignment142) of the two signals due to the diastereotopic methyl groups in the spectrum of the un labeled material. 

Figure 5,20 Portion of a 3D X-filtered NOESY spectrum of uniformly 13C/15N-labeled, stability-enhanced kinaseX in complex with kinaseX inhibitor 2. The protein and inhibitor concentrations used were 300 pM. The F3 (inhibitor1H) plane is at 7.83 ppm. Peaks with protein resonance assignments are labeled. (Note Val-A and Val-B refer to the y-i and y methyl, respectively of the same valine residue.) The spectrum was recorded at 35 °C, 600 MHz 1H frequency using a NOESY mixing time of 100 ms on a Varian Inova spectrometer equipped with a Cold Probe. The spectrum is aliased in the 13C (F2) dimension.

Spectroscopic studies of the enzyme-substrate complex show that the 8-(L-a-aminoadipoyl)-L-cysteinyl-D-valine (ACV) thiolate coordinates to the metal center. First, there is a decrease in the Mossbauer isomer shift of the Fe(II) center from 1.2 to 1.0 mm/sec, indicating a more covalent Fe(II)-ligand environment [195], Second, an intense band appears at 390 nm in the visible spectrum of Cu(II)IPNS upon addition of ACV, which is associated with a thiolate-to-Cu(II) charge transfer transition found for tetragonal copper(II) centers [196], Last, EX-AFS analysis of the Fe(II)IPNS-ACV complex indicates the presence of a sulfur scatterer at ca. 2.3 A, which is a distance typical of Fe(II)-thiolate coordination [197,198], The very recently elucidated crystal structure of the Fe(II)IPNS-ACV complex confirms the thiolate coordination [199],... 

Fig. 8.15. Effect of particle diameter and pore diameter on the separation of 12 PTH-amino acids. Column, 150 x 0.075 mm i.d. packed with 6 pm/300 A or (b) 3.5 pm/80 A Zorbax ODS eluents, (A) 2 mmol/1 ammonium acetate, pH 7.0, (B) 2 mmol/1 ammonium acetate, pH 7.0, 90% acetonitrile gradient elution with 30- 90% B in 15 min flow rate of mobile phase through inlet reservoir, 100 pl/min applied voltage, 20 kV detection, ESI-MS, 0.5 s/spectrum integration time sheath liquid, 1 mmol/1 ammonium acetate, pH 7.0, 90% methanol, 3 pl/min injection, electrokinetic, 2 kV, 2 s sample, PTH-asparagine, PTH-glutamine, PTH-threonine, PTH-glycine, PTH-alanine PTH-tyrosine, PTH-valine, PTH-proline PTH-tryptophan, PTH-phenylalanine, PTH-isoleucine, PTH-leucine (in order of elution). (Reproduced from ref. [113] with permission of the author).

The ES mass spectrum of a tetra-peptide comprised of valine, glycine, serine, and glutamic acid (VGSE) is given in Figure 1.7. VGSE is also an example compound in Chapter 5. The base beak is the [M + 1]+ ion at mlz 391 and the sodium adduct, [M + 23]+, is nearly 90% of the base peak. In addition, there is some useful... 

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