Amides absorption bands

Description of band Cis-amide absorption bands Trans-amide absorption bands... 

Grafts isolated by pepsin and trypsin digestion had stronger amide absorption bands than after pronase digestion. Pronase, because of its broad specificity, is capable of hydrolyzing the collagen trunks more extensively than the other two enzymes. Thus, the grafts isolated by... 

The first observation of such a change was made by Lenormant (1950), who found that deuteration of proteins decreases the intensity of the amide absorption band at 1550cm and results in a new band at 1450cm . This observation was confirmed by the studies of Lenormant and Blout (1953) on the infrared spectra of bovine plasma albumin in D2O. Practical application of this observation was not made however until almost a decade later when simultaneous reports appeared in the literature from different laboratories (Blout et ai, 1961 Nielsen, 1960 Nielsen et al., 1960 and Bryan and Nielsen, 1960). 

Fig. 11.1. Amide absorption bands of a-chymotrypsin (pH. 3.3) at different time intervals after dissolution in DjO ...

I.R. studies are generally not affected by these problems. Especially the spectral regions of the conformationally sensitive amide absorption bands are studied by I.R. spectroscopy. In practice, the best information is obtained from spectra of a diluted solution of small peptides. Spectra in the solid state or from polypeptides show low resolution of interesting absorption bands. 

A solution of the 2-azido ester or amide (ca. 2 g) in a mixture of MeOII (95 mL) and sodium-dried THF (95 mL) was photolyzed under N2 in a Hanovia photochemical reactor (110-W medium-pressure Hg lamp with a Pyrex filter). The reaction was monitored by observing the rate of disappearance of the absorption band (Nf) at 2140 cm 1 (irradiation times of 3-5 h were generally required). When the reaction was complete the solvent was removed in vacuo and the brown residual oil chromatographed on alumina [petroleum ether (bp 60-803C)/benzene 7 3]. Further elution with benzene followed by removal of the solvent gave the product (the esters as pale yellow oils, the amides as crystalline solids), which were further purified by vacuum distillation or by recrysiallization. 

This section also discusses l,5-bcnzodiazepin-2-ones, the corresponding thiones and benzo-diazepinediones. The benzodiazepinones exist in the 1,3-dihydro form 4 A rather than as the 1,5-dihydro tautomers 4B, as shown by 1HNMR spectroscopy.251,252 1Z/-1,5-Benzodiazepine-2,4(3//,5Z/)-diones 5 show NH absorptions at ca. 3180 and 3190, and amide carbonyl bands at ca. 1710 and 1660cm 1.253... 

The polyamides and polyureas exhibited broad, intense N-H stretches around 3300 cm- , a very strong carbonyl stretching vibration was present at 1630 cm- . The amide II band was evident near 1540 cm- . jn addition, sp C-H stretches occurred around 3100 cm- an(j asymmetric and symmetric sp3 c-H stretches at 2950 and 2860 cm- , respectively. The polyurethane showed the carbonyl absorption near 1700 cm-1 and C-0 stretches in the vicinity of... 

In 3, the amino functional group is two methylene units removed from the ferrocene nucleus. It appears from the instantaneous and quantitative formation of h from 3 that this feature minimizes steric effects and also enables 3 to undergo the Schotten-Baumann reaction readily without the classical a-metallocenylcarbenium ion effects providing any constraints. The IR spectrum of showed the characteristic N-H stretch at 3320 cm" (s), the amide 1 (carbonyl) stretch at 1625 an - -(s), the amide II (N—H) stretch at 1540 cm (s), and the amide III band at 1310 cm 1(m). In addition, characteristic absorptions of the ferrocenyl group were evident at 1100 and 1000 cm l (indicating an unsubstituted cyclopentadienyl ring) and at 800 cm"l. 

Fig. 8. Theoretical simulation of VCD (top) and IR absorption (bottom) spectra of alanine dodecapeptides for the amide V bands for a fully a-helical conformation (left) and a fully left-handed 3i-helical conformation (right). The simulations are for the same three isotopically labeled (13C on the amide C=0 for four Ala residues selected in sequence) peptides as in Figure 7 N-terminal tetrad (4AL1), middle (4AL2), and C-terminal (4AL4). The 13C feature is the same for all sequences, confirming the experimentally found unfolding of the C-terminus. The agreement with the shapes in Figure 7 is near quantitative. Reprinted from Silva, R. A. G. D., Kubelka, J., Decatur, S. M., Bour, R, and Keiderling, T. A. (2000a). Proc. Natl. Acad. Sci. USA 97, 8318-8323. 2000 National Academy of Science, U.S.A.

Significantly, the bio-inorganic and polymer-containing PM nanocomposites showed no significant shift in the protein amide I and II vibration bands, or in the characteristic 567 nm optical absorption band of the retinal chromophore of BR, indicating that the structural and dynamical properties of the membrane-bound... 

The study of ZnCFO also was carried out by the method of IR-spectroscopy on spectrometer UR-20. For detection of possible chemical bonds between inorganic and organic components in ZnCFO the spectras of Zn(OH)2, CFO and ZnCFO were studied (fig. 3). As it is shown, IR-spectrum of ZnCFO repeats the characteristic absorption bands of CFO at 3350, 1640 and 1550 cm"1, caused by presence of secondary amide group [5], at the same time the... 

Albertamine, (-)-leontalbamine, and (+)-leontismidine were isolated from Leontice albertii and L. Smirnovii (228,229). They have the same composition, C,5H24N202. The IR spectra of these alkaloids are characterized by the absorption bands giving evidence for the presence of hydroxyl and amide carbonyl groups. There is also absorption (except in the albertamine spectrum) in the region of 2700-2800 cm attributed to trans-quinolizidine systems. The UV spectra show absorption maxima at 220 nm. 

Complexes of rhenium(bipyridine)(tricarbonyl)(picoline) units linked covalently to magnesium tetraphenylporphyrins via an amide bond between the bipyridine and one phenyl substituent of the porphyrin 19 exhibited no signs of electronic interaction between the Re(CO)3(bpy) nnits and the metalloporphyrin units in their gronnd states. However, emission spectroscopy revealed a solvent-dependent quenching of porphyrin emission upon irradiation into the long-wavelength absorption bands localized on the porphyrin. 

The wavelengths of IR absorption bands are characteristic of specific types of chemical bonds. In the past infrared had little application in protein analysis due to instrumentation and interpretation limitations. The development of Fourier transform infrared spectroscopy (FUR) makes it possible to characterize proteins using IR techniques (Surewicz et al. 1993). Several IR absorption regions are important for protein analysis. The amide I groups in proteins have a vibration absorption frequency of 1630-1670 cm. Secondary structures of proteins such as alpha(a)-helix and beta(P)-sheet have amide absorptions of 1645-1660 cm-1 and 1665-1680 cm, respectively. Random coil has absorptions in the range of 1660-1670 cm These characterization criteria come from studies of model polypeptides with known secondary structures. Thus, FTIR is useful in conformational analysis of peptides and proteins (Arrondo et al. 1993). 

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