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Amide band

A criterion for the position of the extent of the mesomerism of type 9 is given by the bond order of the CO bond, a first approximation to W hich can be obtained from the infrared spectrum (v C=0). Unfortunately, relatively little is known of the infrared spectra of amide anions. How-ever, it can be assumed that the mesomeric relationships in the anions 9 can also be deduced from the infrared spectra of the free amides (4), although, of course, the absolute participation of the canonical forms a and b in structures 4 and 9 is different. If Table I is considered from this point of view, the intimate relationship betw-een the position of the amide band 1 (v C=0) and the orientation (0 or N) of methylation of lactams by diazomethane is unmistakeable. Thus the behavior of a lactam tow ard diazomethane can be deduced from the acidity (velocity of reaction) and the C=0 stretching frequency (orientation of methylation). Three major regions can be differentiated (1) 1620-1680 cm h 0-methylation (2) 1680-1720 cm i, O- and A -methylation, w ith kinetic dependence and (3) 1730-1800 em , A -methylation, The factual material in Table I is... [Pg.253]

The extent of restricted rotation about the amide band of (38) was used to compare the electron-withdrawing process of phosphonium salts (38, Y = alkyl) and chalcogenides (38, Y = O or S) with the more conventional electron-withdrawing groups. These phosphorus groups were found to exert a — A7 effect comparable with that of a nitro-group. [Pg.259]

Data concerning plants of occurrence, melting points, and spectral features of these alkaloids have been collected by Krane et al. (6). Some characteristic spectral features deserve attention. In IR spectra the amide band appears in the region between 1670 and 1646 cm-1. Among the H-NMR spectra, singlets of the N-methyl amide protons are situated between 82.91 and 3.27, and the... [Pg.294]

Figure 12 IR transmission images of a polymer laminate. Left video image. Right IR image of the amide band (bright high COPA concentration). Only the COPA layers are visible in the FTIR image. The horizontal features in the middle layer are holes, originating during microtoming due to the material s softness. Figure 12 IR transmission images of a polymer laminate. Left video image. Right IR image of the amide band (bright high COPA concentration). Only the COPA layers are visible in the FTIR image. The horizontal features in the middle layer are holes, originating during microtoming due to the material s softness.
The UV spectrum [Amax 243, 267 (sh), 292, 322 (sh), 335, 356, and 372 nm] of (+)-staurosporine (AM-2282) (295) was very similar to that of staurosporinone (293), indicating the presence of a similar indolo[2,3-fl]pyrrolo[3,4-c]carbazole framework. The IR spectrum indicated the presence of an NH band at v ax 3500 cm and an amide band at 1675 cm . The structure and relative stereochemistry of this isolate were established by X-ray crystallographic analysis of the methanol solvate (282,283). The structure 295, indicating the presence of an indolocarbazole subunit, wherein two... [Pg.115]

Due to limitations in signal-to-noise ratio available for the then common dispersive IR instruments, peptide and protein vibrational spectroscopic studies shifted to emphasize Raman measurements in the 1970s 29-32 Qualitatively the same sorts of empirical correlations as discussed above have been found between frequencies of amide bands in the Raman and secondary structure. However, due to the complementary selection rules for Raman as compared to IR and to the multi-component nature of these polymeric spectral bands, the... [Pg.715]

Miyazawa, T., In Characteristic Amide Bands and Conformations of Polypeptides, Stah-mann, M. A., Ed. University of Wisconsin Madison, WI, (1962) p 201. [Pg.733]

Of system 3, a trialkyl derivative and a 3-carbamoyl derivative,108 the latter having amide bands at 1675 and 1623 cm 1, 5-chloro-3-amino-and 7-thiol derivatives208, 5-substituted trifluoromethyl derivatives,98 and 5-chloro-3-substituted (including 3-amino) derivatives81... [Pg.111]

The infrared spectrum of rabbit hair was similar to that of the wool fibers with readily apparent amide bands in the regions of 1650 cm-1 and 1530 cm-1 (Figure 6). [Pg.60]

The isoselenazole ring in unsubstituted 3-hydroxy-l-benzo-l,2-selenazole (26) and in its 7-azaanalog (27) exists in nonaromatic amide form such as in 28 or 29 (Scheme 4). The amide proton is easily exchanged, via potassium salt, by alkyl, acyl, or sulfonyl groups. The additional evidence for amide structure is based on spectral data. For example, the amide band nc=0 = 1646 cm 1 in the IR spectrum and the broad singlet at 9.34 ppm in the 11 NMR spectrum were observed for 29 [49-51],... [Pg.294]

Simulations of amide bands for a /1-sheet oriented parallel to the interface with different angles of incidence and use of p-polarized light are shown in Fig. 8. Comparison of measured and simulated spectra reveals that amyloid-] (Ap) is lying almost flat at the air-water interface, although a slightly tilted conformation cannot be excluded. [Pg.258]

Vibrational spectroscopy has been used in the past as an indicator of protein structural motifs. Most of the work utilized IR spectroscopy (see, for example, Refs. 118-128), but Raman spectroscopy has also been demonstrated to be extremely useful (129,130). Amide modes are vibrational eigenmodes localized on the peptide backbone, whose frequencies and intensities are related to the structure of the protein. The protein secondary structures must be the main factors determining the force fields and hence the spectra of the amide bands. In particular the amide I band (1600-1700 cm-1), which mainly involves the C=0-stretching motion of the peptide backbone, is ideal for infrared spectroscopy since it has an large transition dipole moment and is spectrally isolated... [Pg.318]

We model the amide band as a system of N interacting localized vibrations. For the sake of third-order spectroscopies, we only need to consider the lowest three levels of each peptide group with energies 0, Gm, Gnl(m = 1,..., N). The matrix elements of the dipole operator corresponding to the 0-1 and 1-2 transitions are denoted /j.m and //ra, respectively, and their ratio is Km = To introduce the vibrational Frenkel exciton model,... [Pg.368]

Melinonine B is formulated as C2oH2 N20+ on the basis of analyses of the chloride, iodide, and perchlorate the chloride, mp 311° (dec.), has [a]D —14.8° (methanol-water) (54). The alkaloid has one A-methyl group but no methoxyl or (7-methyl groups. Its UV-spectrum is that of a 2,3-disubstituted indole and its IR-spectrum exhibits both hydroxyl (3.05 /x) and N—H (3.20 /x) absorption. Acetylation of melinonine B gives a crystalline 0,A-diacetyl derivative which results from attack at the indolic Na, since the UV-spectrum of this derivative is that of an A-acylindole and its IR-spectrum has both ester and amide bands. [Pg.529]

Although standard IR spectrometers are used for studying the amide bands, FTIR spectrometers are more accurate and reliable. FT-IR spectrophotometers are based upon the Michelson interferometer. A typical instrument (Fig. 7.1) comprises an optical bench housing the interferometer, sample, infrared source and detector, coupled to a computer, which controls the spectral scanning, analysis and data processing (for review see Griffiths, 1980). [Pg.210]

The first data showing a transmembrane barrel came from electron microscopy and electron diffraction of two-dimensional porin crystals (Jap, 1989). They followed spectroscopic studies of the amide bands in the infrared range indicating that the porin contains /1-strands tilted at a 45° angle against the membrane plane (Nabredyk et al., 1988). As... [Pg.52]

The infrared spectra (11,12) can be used advantageously to provide a facile procedure to characterize polyamides in the untreated and treated states. Structure-frequency correlations have been established which indicate that the a form and y form can be clearly distinguished using two amide bands characteristic of the structure of the polyamide. These are ... [Pg.32]

UV resonance Raman spectroscopy (UVRR), Sec. 6.1, has been used to determine the secondary structure of proteins. The strong conformational frequency and cross section dependence of the amide bands indicate that they are sensitive monitors of protein secondary structure. Excitation of the amide bands below 210 nm makes it possible to selectively study the secondary structure, while excitation between 210 and 240 nm selectively enhances aromatic amino acid bands (investigation of tyrosine and tryptophan environments) (Song and Asher, 1989 Wang et al., 1989, Su et al., 1991). Quantitative analysis of the UVRR spectra of a range of proteins showed a linear relation between the non-helical content and a newly characterized amide vibration referred to as amide S, which is found at 1385 cm (Wang et al., 1991). [Pg.358]


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See also in sourсe #XX -- [ Pg.208 ]

See also in sourсe #XX -- [ Pg.114 , Pg.115 , Pg.116 , Pg.117 , Pg.118 , Pg.119 , Pg.120 , Pg.121 , Pg.122 , Pg.123 , Pg.124 , Pg.125 , Pg.151 , Pg.152 ]




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Amid I band

Amide A band

Amide B band

Amide I and II bands

Amide I band

Amide II band

Amide III band

Amide IV band

Amide Raman bands

Amide V band

Amide VI band

Amide secondary, combination bands

Amides absorption bands

Amides infrared absorption band positions

Analysis of the Amide I Band

Band assignments amides

Combination bands amides

N-H combination band from primary amides

N—H Bending Vibrations (Amide II Band)

Protein secondary amide bands

Proteins amide I band

The Amide I and II bands

The Amide II Band

The amide III band

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