Infrared-spectral characteristics of some acetylated,anomeric glycosides

Barker and co-workers had described the C-1-H deformation bands in the ranges 844 ±8 cm^?1 and 891 ±7 cm^?1 as characteristic bands for the α and β anomers, respectively, of hexo- and pento-pyranoses and -pyranosides, and their derivatives. Later, Audichya and co-workers reported the presence of the 844 ±8-cm^?1 band for both anomers of some aryl d-glucoside derivatives, making the applicability of the earlier findings doubtful. Examination by us of the i.r. spectra of some aryl glycoside derivatives suggested that the origin of the band at 844 ±8 cm^?1 for the β anomers of the p-substituted-aryl glycoside derivatives studied by Audichya et al. could be a CH, out-of-plane deformation-mode of the substituted aromatic ring. Also, their further claim of a characteristic band in the region 961-957 cm^?1 for α anomers is shown to be of little diagnostic value. The relative intensities of bands in the COC stretching region, 1100-1000 cm^?1, and a band near 300 cm^?1 in the COC deformation region, found only for the β anomers, are shown to be helpful in differentiating the anomers of some peracetylated alkyl and aryl glycosides.     

A vitrational study of poly (L-proline) I and II in the far infrared.

The far infrared spectra of poly(L -proline) I (190–35 cm^?1) and II (400–35 cm^?1) were obtained in the solid state at both 300° and 110°K. A significant difference in the region below 100 cm^?1 was observed. A very intense band located at 60 cm^?1 in the infrared spectrum of form II has no counterpart in form I. This indicates the sensitivity of low-frequency vibrations to the difference in conformation assumed by both forms in the solid state. Additional bands observed in this study are correlated with ir and Raman data previously reported and tentative assignments are made using the results of normal mode calculations (in the single-chain approximation) which have been reported.     

Dark respiration of the stipe of Ecklonia cava (Laminariales, Phaeophyta) in relation to temperature

Sporophytes of Ecklonia cava Kjellman (Laminariales, Phaeophyta) with a stipe length of 22–102 cm were collected at 6–9 m depth in Nabeta Bay, Shimoda, central Japan by scuba diving in February (winter) and in August (summer) 1998. Dark respiration of the intact stipe of E. cava was measured at various water temperatures ranging from 15 to 27.5°C in winter and 15–30°C in summer in a closed system by using a dissolved oxygen meter. The stipe respiration was compared on whole stipe, length, surface area, volume, wet weight and dry weight bases. On each basis, the stipe respiration always increased with a rise in water temperature within the temperature range investigated. The stipes showed similar respiration rates on each basis of length, surface area, volume, wet weight and dry weight at each temperature, irrespective of the stipe length. The mean respiration rates in winter (at 15–27.5°C) were: length, 16.7–32.5 μL O₂ cm^?1 h^?1; surface area, 3.2–6.2 μL O₂ cm^?2 h^?1; volume, 7.6–15.0 μL O₂ cm^?3 h^?1; wet weight, 6.2–12.2 μL O₂ g (wet weight)^?1 h^?1; and dry weight, 43.8–88.0 μL O₂ g (dry weight)^?1 h^?1. Those for summer (at 15–30°C) were: length, 17.1–32.0 μL O₂ cm^?1 h^?1; surface area, 3.6–6.8 μL O₂ cm^?2 h^?1; volume, 9.7–18.7 μL O₂ cm^?3 h^?1; wet weight, 7.6–14.6 μL O₂ g (wet weight)^?1 h^?1; and dry weight, 49.4–95.8 μL O₂ g (dry weight)^?1 h^?1. This is the first report of the intact stipe respiration of E. cava at various temperatures.     

Complex biopolymeric systems at stalk/epicuticular wax plant interfaces: A near infrared spectroscopy study of the sugarcane example

Naturally occurring macromolecules present at the epicuticular wax/stalk tissue interface of sugarcane were investigated using near infrared spectroscopy (NIRS). Investigations of water, cellulose, and wax‐cellulose interrelationships were possible using NIRS methods, where in the past many different techniques have been required. The sugarcane complex interface was used as an example of typical phenomena found at plant leaf/stalk interfaces. This detailed study showed that sugarcane cultivars exhibit spectral differences in the CH_n, water OH, and cellulose OH regions, reflecting the presence of epicuticular wax, epidermis, and ground tissue. Spectrally complex water bands (5276 cm^?1 and 7500–6000 cm^?1) were investigated via freeze‐drying experiments which revealed sequentially a complex band substructure (7500–6000 cm^?1), a developing weak H‐bonding system (～7301 cm^?1), and strong H‐bonding (～7062 cm^?1) assigned to water—cellulose interactions. Principal component analysis techniques clarified complex band trends that developed during the desorption experiment. Bands from wax‐free stalk were minimized in the 4327–4080 cm^?1 region (C? H_n vibrational modes associated with long chain fatty compounds), while bands from the stalk tissue (particularly lignin and moisture) became more pronounced. This work is a comprehensive guide to similar studies by scientists involved in a variety of plant and fiber research fields. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 642–651, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Raman spectroscopic studies of different forms of cholesterol and its derivatives in the crystalline state

A Raman spectroscopic study has been carried out on a number of cholesterols and cholesterol derivatives in the crystalline state, in order to obtain some empirical correlations between the Raman spectra and structure of each cholesterol form.Although the Raman spectra of the various cholesterols are highly complex it was found that three regions of the spectrum yield considerable information about the crystalline chain packing in each form. They are: (1) the low frequency region below 300 cm^?1, giving information on the inter- and intramolecular vibrations in the cholesteryl moiety; (2) the methylene rocking/deformation region between 1400 and 1500 cm^?1 giving information on chain packing in the crystalline state, and (3) the C–H stretching region between 2700 and 3100 cm^?1 which appears to indicate that there is a correlation between branching in the side chains of the cholesterols, polarity of the substituent groups in the various derivatives studied and relative chain order in the packing arrangements in the crystalline state.A study of two branched chain aerosol derivatives, bis(di-2-octyl)sodium sulphosuccinate and its isomer bis(di-2-ethylhexyl)sodium sulphosuccinate, indicate that branched chain amphiphiles are good Raman spectroscopic models for the cholesterols, similar to previous Raman spectroscopic studies which have found straight chain amphiphiles to be good models for more complex phospholipids.     

Changes in Raman vibrational bands of calf thymus DNA during the B-to-A transition

The B -to-A conformational transition of calf thymus DNA fibers was followed employing Raman spectroscopy. The transition was induced by soaking DNA fibers in water/ethanol mixtures increasing from 60 to 85% ethanol (v/v). Intensity changes of 17 Raman vibrational bands were quantified in the region from 400 to 860 cm^?1. Two bands at 500 and 784 cm^?1 were employed as internal standards. These bands do not appear to change in intensity with ethanol concentration. Large intensity changes relative to these two bands are observed between 70 and 74% ethanol for backbone vibrations at 708, 808, and 835 cm^?1, and base vibrations at 682, 730, and 750 cm^?1. These results indicate that a highly cooperative conformational change takes place between different portions of DNA in the B -to-A transition. Relative intensity changes preceding the onset of the major transition are observed in only two bands; at 835 cm^?1, assigned to a ribose–phosphate vibration, and at 750 cm^?1, assigned to thymine. The implications of these pretransition changes are discussed.     

An infrared study of various nitrated polysaccharides and their structural characterisation

Infrared absorption spectra for a number of polysaccharides and their nitrated derivatives have been obtained. The frequency range 730–960 cm^?1 is useful for identification of the polysaccharides, and the region 900–1350 cm^?1 is more suitable for distinguishing the nitrated materials. The strong intensity of the nitrate bands limits the interpretation of spectra below 960 cm^?1, but above this frequency the absorption bands of nitrated polysaccharides are generally sharper and more clearly defined than the corresponding bands of the parent polysaccharides. Data on the COC bridge, CC ring, CO, and COH frequencies and on the CH deformation and stretching frequencies have been obtained. The use of i.r. spectroscopy for the quantitative determination of nitrate groups in nitrated polysaccharides is discussed.     

Raman studies of conformational changes in model membrane systems

Laser Raman spectra of concentrated samples of phosphatidyl choline and phosphatidyl ethanolamine were taken at approximately 10° intervals over a temperature range of 90°–19°C. The spectral region from 30 to 3300 cm^?1 was investigated. Several new spectral features were discovered which are correlated to phospholipid liquid crystalline structure. It is shown that 1) frequency shifts occur in the $\text{PO}{}_2{}^{\mathrm{?}}$ symmetric stretch band which suggest a change in exposure of the PO₂ group to the solvent upon melting, 2) the frequency of the translational hydrocarbon mode around 150 cm^?1 appears to indicate the degree to which the hydrocarbon chain is extended, 3) the methyl and methylene stretch bands at 2890 and 2850 cm^?1 very clearly demonstrate hydrocarbon chain melting, and 4) the 720 cm^?1 band, previously assigned to the symmetric OPO diester stretch, appears to be due instead to the symmetric CN stretch of choline.     

Vibrational Raman optical activity of alanyl peptide oligomers: A new perspective on aqueous solution conformation

The vibrational Raman optical activity (ROA) spectra of di- and tri-L -alanine in the range 650–1750 cm^?1 have been measured in H₂O and D₂O solution at high, neutral, and low pH and pD. Corresponding ROA spectra for tetra- and penta-L -alanine have also been obtained, but over a more restricted set of pH and pD conditions. There are similarities with the ROA spectrum of L -alanine below ～ 1200 cm^?1, but the spectra are very different above this wavenumber due to the influence of the vibrational coordinates of the peptide group. The similar overall appearance of the di-, tri-, and tetrapeptide ROA under selected conditions of pH and pD, and of all four peptide ROA spectra in DCl and HCl solutions, in the backbone skeletal stretch region ～ 1050–1200 cm^?1 and the extended amide III region ～ 1250–1350 cm^?1, suggests that the backbone conformation is approximately the same in all four structures. One difference, however, is a shift of a large positive ROA band in H₂O at ～ 1341 cm^?1 in the dipeptide, assigned to C_α–H and in-plane N–H deformations, down to ～ 1331 cm ^?1 in the tripeptide and to ～ 1315 cm^?1 in the tetrapeptide and pentapeptide (the last in HCl due to insufficient solubility in H₂O), which indicates increasing delocalization of the corresponding normal mode with increasing chain length. Our results do not support the suggestion that stabilizing interactions of the zwitterionic end groups in tri-L -alanine at neutral pH leads to a different solution structure to that at high pH. © 1994 John Wiley & Sons, Inc.     

Low-frequency infrared bands and chain conformations of polypeptides

Infrared spectra of polypeptides were measured in the region of 1800–400 cm^?1. For the α-helical form, disordered form, and antiparallel-chain β-form, amide V band- arising from N-H out-of-plane bending models were observed at 610–620, around 650, and 700–705 cm^?1, respectively, and amide V′ bands arising from N-D out-of-plane bending modes were observed at 455–465, around 510, and a 515–530 cm^?1, respectively. These correlations are useful for conformation diagnoses, particularly for copolyamino-acids or proteins which are not oriented. The nature of low-frequency amide bands are discussed with reference to potential energy distributions calculated for the α-helical form and β form.     

Structural analysis of some soluble elastins by means of FT‐IR and 2D IR correlation spectroscopy

Fourier transform infrared (FT‐IR) spectroscopy combined with 2D correlation spectroscopy has been used to offer some information about stability and structure of some soluble elastins. Temperature has been chosen as the perturbation to monitor the infrared behavior of various soluble elastins, namely, α‐elastin p, α‐elastin, and k‐elastin. In the 3800–2700 cm^?1 region, the H‐containing groups were analyzed. The bonded hydroxyls are found to decrease prior to the NH‐related hydrogen bonds and also to the conformational reorganization of hydrocarbon chains. The transition temperatures were evaluated and they were found to agree with those obtained from DSC data. The FTIR spectra and their 2nd derivatives denote that α‐ elastins exhibited amide‐I, ‐II and ‐III bands at 1656, 1539 and 1236 cm^?1, respectively, while in k‐elastin these bands were found at 1652 cm^?1 for amide I, 1540 cm^?1 for amide II and 1248 cm^?1 for amide III. The macroscopic IR finger‐print method, which combines: general IR spectra, secondary derivative spectra, and 2D‐IR correlation spectra, is useful to discriminate different elastins. Thus using the differences of the position and intensity of the bands from “fingerprint region” of studied elastins, which include the peaks assigned to C?O, C? C groups from α‐helix, β‐turn, and the peaks assigned to the amide groups, it is possible to identify and discriminate elastins from each others. Furthermore, the pattern of 2D‐IR correlation spectra under thermal perturbation, allow their direct identification and discrimination. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 1072–1084, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Estimation of poly A secondary structure from Raman scattering in acid aqueous solution.

In the frequency region 600–1600 cm^?1 the Raman spectra of acidic aqueous solutions of poly (rA) consist of several well-resolved lines. Four of these lines at 725, 1303, 1336 and 1508 cm^?1 demonstrate the Raman hypochromic effect of poly (rA) at pH-values of 5.73 and 5.35 as a function of the temperature.The results suggest that Raman intensity measurements are sensitive to order-disorder transitions of aqueous polynucleotides.     

Raman spectroscopic study of tropomyosin denaturation

Raman spectra of the pH denaturation of tropomyosin are presented. In the native state tropomyosin has an alpha-helical content of nearly 90%, but this value drops rapidly as the pH is raised above 9.5. The Raman spectrum of the native state is characterized by a strong amide I line appearing at 1655 cm^?1, very weak scattering in the amide III region around 1250 cm^?1, and a medium-intensity line at 940 cm^?1. When the protein is pH-denatured, a strong amide III line appears at 1254 cm^?1 and the 940 cm^?1 line becomes weak. The intensities of the latter two lines are a sensitive measure of the alpha-helical and disordered chain content. These results are consistent with the helix-to-coil studies of the polypeptides. The Raman spectra of α-casein and prothrombin, proteins thought to have little or no ordered secondary structure, are investigated. The amide III regions of both spectra display strong lines at 1254 cm^?1 and only weak scattering is observed at 940 cm^?1, features characteristic of the denatured tropomyosin spectrum. The amide I mode of α-casein appears at 1668 cm^?1, in agreement with the previously reported spectra of disordered polypeptides, poly-L -glutamic acid and poly-L -lysine at pH 7.0 and mechanically deformed poly-L -alanine.     

The detection of food soils on stainless steel using energy dispersive X-ray and Fourier transform infrared spectroscopy

Organic soiling is a major issue in the food processing industries, causing a range of biofouling and microbiological problems. Energy dispersive X-ray (EDX) and Fourier transform infra red spectroscopy (FT-IR) were used to quantify and determine the biochemical groups of food soils on stainless steel surfaces. EDX quantified organic material on surfaces where oily based residues predominated, but was limited in its usefulness since other food soils were difficult to detect. FT-IR provided spectral ‘fingerprints’ for each of the soils tested. Key soiling components were associated with specific peaks, viz. oils at 3025 cm^?1–3011 cm^?1, proteins at 1698 cm^?1–1636 cm^?1 and carbohydrates at 1658 cm^?1–1596 cm^?1, 783 cm^?1–742 cm^?1. High concentrations of some soils (10%) were needed for detection by both EDX and FT-IR. The two techniques may be of use for quantifying and identifying specific recalcitrant soils on surfaces to improve cleaning and hygiene regimes.     

Raman intensities of carbon-carbon stretching modes in a model membrane

Laser-Raman spectra of L-α-dimyristoylphosphatidylcholine (DMPC) liposomes in the spectral range 1000–1200 cm^?1 were obtained as a function of temperature from ?80 to +50°C. The triplet found in this spectral region was resolved into Lorentzian components by means of an iterative computer program. The peak intensities, band widths, and band areas of the resolved 1062 cm^?1 and 1130 cm^?1 bands, assigned to CC stretching vibrations of trans segments, were evaluated as a function of temperature. While the peak intensities of the bands decrease substantially with temperature, the band widths show a considerable increase. The change in band areas is therefore smaller than the change in peak heights. Experiments with all trans carboxylic acids showed that in these compounds the area of the Raman bands at 1062 cm^?1 and 1130 cm^?1 is proportional to the number of trans bonds. The variation with temperature of the number of trans and gauche bonds in the studied phospholipid is reflected by the change of the area of the 1130 cm^?1 Raman band.     

Use of Fourier-transform infrared spectroscopy in the diagnosis of rheumatoid arthritis: a pilot study

Rheumatoid arthritis is an autoimmune inflammatory disease leading to joint cartilage, bone degradation and limitation of mobility. Diagnosis of RA is difficult and complex. There are also no effective methods for clear discrimination between RA patients and non-RA individuals. In this work we use IR spectroscopy to differentiate RA patients and blood donors’ sera. We found differences between investigated sera (RA and non-RA) in range of 3000–2800 and 1800–800 cm^?1 (W1–W5 regions). Based on mathematical analysis we developed a K-NN model characterized by 85?% of sensitivity and 100?% of specificity. Also we found that, wavenumber 1424 cm^?1, comprising in W3 region, was the most effective in human sera distinguishing. We conclude that IR spectroscopy may serve as a fast and easy method useful in RA serology.     

Resonance raman study of the heme-linked ionization in reduced horseradish peroxidase

The resonance Raman spectra of reduced horseradish peroxidase (oxidoreductase, EC 1.11.1.7) and its cyanide complex in the 200–600 cm^?1 region were measured. Among many Raman lines observed, only the line at 244 cm^?1 (pH 6.5) exhibited the pH dependent frequency shift. This line disappeared in the cyanide complex. The 244-cm^?1 line was intense upon excitation at 441.6 nm but unrecognizable at 488.0 nm. Consequently this line is assignable to the Fe-N_ε (His, proximal) stretching mode in accord with the 220-cm^?1 line of the Fe-N_ε (His F8) stretching line of deoxy Mb. It is concluded that the ionization of an amino acid residue with pK_a = 7.17 is transmitted to heme $\text{via}$ Fe-N_ε (His) bond in the proximal side.     

Steric structure of L-proline oligopeptides. I. Infrared absorption spectra of the oligopeptides and poly-L-proline

Poly-L -prolines I and II were differentiated by the characteristic bands in the far infrared region. Form I showed two broad bands at about 280 and 160 cm^?1 and form II two bands at, 400 and 670 cm.^?1. Furthermore, three broad bands at about 250, 200, and 100 cm.^?1 were observed in the spectrum for form II. Infrared absorption bands of the pentamer, hexamer, and octamer of tert-amyloxycarbonyl-L -proline were almost similar to those of poly-L -proline II in the 1800–75 cm.^?1 region. In the far-infrared region, especially, the absorption bands of these three oligopeptides were in good agreement with that of poly–L –proline II. Accordingly we concluded that the molecules of pentamer, hexamer, and octamer had a helical structure of a left-handed threefold screw axis. The tetrapeptide of tert-amyloxycarbonyl-L -proline might also have a left-handed helix, probably one turn, since the tetramer clearly showed an absorption band at about 400 cm.^?-1 characteristic of poly–L –proline II.     

Far-infrared spectra of some globular proteins

The far-infrared absorption spectrum (40–400 cm^?1) of solid pellets and films of several globular proteins (lysozyme, myoglobin, hemoglobin, serum albumin, ribonuclease, chymotrypsinogen, subtilisin) and of some representative polypeptides [nylon 66, poly (γ-benzyl L -glutamate)] have been investigated by using a Michelson interferometer. While polypeptides are known to present several peaks which can be assigned mostly to hydrogen-bond modes, all the investigated globular proteins display only one broad, intense baud in the 100–200 cm^?1 region. The origin of this band, which persists even after denaturation or partial digestion, is discussed.     

Infrared absorption and raman scattering of sulfate groups of heparin and related glycosaminoglycans in aqueous solution

The i.r. spectra for aqueous solutions of sulfated glycosaminoglycans and model compounds in the transmittance “window” region of the solvent (1400-950 cm^?1) are dominated by the strong and complex absorption centered at ～1230 cm^?1 and associated with the antisymmetric stretching vibrations of the SO groups. Primary and secondary O-sulfate groups absorb at somewhat higher frequencies (1260-1200 cm^?1) than N-sulfates (～1185 cm^?1). Each sulfate band lends itself to quantitative applications, especially within a given class of sulfated polysaccharide. Laser-Raman spectra of heparin and model compounds have been obtained in aqueous solution and in the solid state. The most-prominent Raman peak (at ～1060 cm^?1) is attributable to the symmetrical vibration of the SO groups, with N-sulfates emitting at somewhat lower frequencies (～1040 cm^?1) than O-sulfates. The Raman pattern in the 950-800 cm^?1 region (currently used in the i.r. for distinguishing between types of sulfate groups) also involves vibrations that are not localized only in the COS bonds.