Infrared Spectral Changes Research Articles

Physiochemical aspects for the adsorption behavior of sodium carboxymethyl cellulose onto mesoporous granular fine quartz surface from its aqueous solutions

ABSTRACT The present study focused onto adsorptive properties and nature of the interaction between sodiumcarboxymethylcellulose (NaCMC) and mesoporous granular fine quartz (MGFQ) applying various in-depth characterization techniques, adoption isotherm models including statistical aspects and operation variables. The physiochemical parameters of MGFQ such as specific surface area (SBET )=11.34 m2/g, pore volume (Vp)=0.09 cm3/g, total pore volume (Vtp)=0.09 cm3/g, mean pore diameter=32.52nm were determined. The thermal result revealed that NaCMC could be used at moderate temperature (251°C), which was suitable for its application. The equilibrium isotherm data were fitted with Langmuir, Freundlich, Temkin and Jovanovic model of adsorption and compered by linear determination coefficient (R2), obeyed the order as Freundlich (R2=0.9984)> Langmuir (R2=0.9194)>Temkin (R2=0.8899)>Jovanovic (R2=0.8709). The infra-red spectral changes in the region 1104cm−1 and 1076cm−1 suggested that NaCMC accumulation onto MGFQ was stabilized by H-bonding and some other weak noncovalent interactions depending on the solution optimized conditions.

Using chemometrics to characterise and unravel the near infra-red spectral changes induced in aubergine fruit by chilling injury as influenced by storage time and temperature

The early non-destructive detection of chilling injury (CI) in aubergine fruit was investigated using spectroscopy. CI is a physiological disorder that occurs when the fruit is subjected to temperatures lower than 12 °C. Reference measurements of CI were acquired by visual appearance analysis, measuring electrolyte leakage (EL), mass loss and firmness evaluations which demonstrated that even before three days of storage at 2 °C, the CI process was initiated. An ANOVA-simultaneous component analysis (ASCA) was used to investigate the effect of temperature and storage time on the Fourier transform – near infra-red (FT-NIR) spectral fingerprints. The ASCA model demonstrated that temperature, duration of storage, and their interaction had a significant effect on the spectra. In addition, it was possible to highlight the main variations in the experimental results with reference to the effects of the main factors, and with respect to storage time, to discover any major monotonic trends with time. Partial least squares-discriminant analysis (PLS-DA) was used as a supervised classification method to discriminate between fruit based on chilling and safe temperatures. In this case, only significant spectral wavebands which were significantly influenced by the effect of temperature based on ASCA were utilised. PLS-DA prediction accuracy was 87.4 ± 2.7% as estimated by a repeated double-cross-validation procedure (50 runs) and the significance of the observed discrimination was verified by means of permutation tests. The outcomes of this study indicate a promising potential for near infra-red spectroscopy (NIRS) to provide non-invasive, rapid and reliable detection of CI in aubergine fruit.

Specific and non-specific interactions between metal cations and zwitterionic alanine tripeptide in saline solutions reported by the symmetric carboxylate stretching and amide-II vibrations.

The "specific" interaction between metal cations (Na+, Ca2+, Mg2+, and Zn2+) and the charged COO- group, and the "non-specific" interaction between these cations and the peptide backbone of a zwitterionic trialanine (Ala3) in aqueous solutions were examined in detail, using linear infrared (IR) absorptions of the COO- symmetric stretching and the amide-II (mainly the C-N stretching) modes as IR probes. Different IR spectral changes in peak positions and intensities of the two IR probes clearly demonstrate their sensitivities to nearby cation distributions in distance and population. Quantum chemistry calculations and molecular dynamics simulations were used to describe the cation-peptide interaction picture. These combined results suggest that Na+ and Ca2+ tend to bind to the COO- group in the bidentate form, while Mg2+ and Zn2+ tend to bind to the COO- group in the pseudo-bridging form. The results also show that while all three divalent cations indirectly interact with the peptide backbone with large population, Ca2+ and Mg2+ can be sometimes distributed very close to the backbone. Such a non-specific cation interaction can be moderately sensed by the C-N stretching of the amide-II mode when cations approach the polar amide C[double bond, length as m-dash]O group, and is also influenced by the NH3+ charge group located at the N-terminus. The results suggest that the experimentally observed complication of the Hofmeister cation series shall be understood as a combined specific and non-specific cation-peptide interactions.

Comparative Physicochemical Study of the Thermally and Thermo-oxidatively Decomposed Automotive Crankcase Oils

The performance characteristics of the automotive crankcase oil, be it of synthetic or natural origin is basically a function of its stability at the engine operation temperature. The performance characteristics usually drop with aging occasioned by a combination of thermal and thermo-oxidative decomposition. The two modes oil degradation have been investigated by simulating those conditions encountered in the automotive crankcase engines under normal operation. Two commercially available multigrade crankcase lubricants (synthetic oil and mineral blend) were subjected to thermal and thermo-oxidative decomposition using a modified version of the turbine oil oxidation test apparatus. Thermal decomposition was carried out in the absence of air while thermo-oxidative degradation was achieved with an air flow rate of 1.0 litre per hour for 15hours. The physicochemical changes in oil composition were evaluated by measuring the Total Acid Number (TAN), Total Oxidation Products (TOP) and the infra-red spectral changes of the decomposition products at various temperatures ranging from 100°C to as high as 380°C. The results indicated that the mineral oil showed a higher aging characteristics in both the thermal and thermo-oxidative decomposition than its synthetic multigrade counterpart. The infra-red analysis revealed that the physicochemical changes associated with aging of the oil samples at high temperature were mainly due to the breakdown of additives and hydrocarbon matrix at the onset of aging into monomeric fragments of peroxides, organic acids and carbonyl compounds which polymerize at a much higher temperature into dark resinous materials. The physicochemical changes with temperature may therefore be used in evaluating the temperature-related aging hence the thermal and thermooxidative stabilities as well as the performance characteristics of crankcase lubricants.

On the origin of IR spectral changes upon protein folding

The unfolded- and folded-state infrared (IR) spectra of peptides studied to date show a common pattern, i.e., the amide I peak of the unfolded state is typically shifted toward higher frequencies with respect to the folded peak. Here, we study by means of a theoretical–computational method, the Perturbed Matrix Method (PMM), the IR spectra in the amide I region of two β -hairpin peptides. The computed spectra are in good agreement with the experimental ones, thus providing an explanation of the physical origin underlying the differences of the unfolded- and folded-state spectra.

In situ Study of DNA Attachment and Hybridization at Silicon Surfaces by Infrared Absorption Spectroscopy

In this study, we have investigated in situ the process of DNA immobilization and the subsequent hybridization on Si surfaces by using infrared (IR) absorption spectroscopy in the geometry of multiple internal reflection (MIR-IRAS). We use 3-aminopropyl-triethoxysilane (APTES) to functionalize Si surfaces with the amine group for DNA attachment. MIR-IRAS data, together with ab initio calculations, demonstrate that the amine-terminated surfaces are covalently coupled to thiol-modified oligonucleotides using a crosslinker of sulfo-succinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SSMCC). Hybridization experiments reveal that MIR-IRAS enables us to detect DNA hybridization through IR spectral changes in the frequency region around 1685 cm-1 where the vibrational modes of the bases appear. The present results show that MIR-IRAS is a promising tool for the label-free detection of DNA hybridization as well as the in situ (in vitro) characterization of the conformation changes of DNA molecules immobilized on Si surfaces.

IR spectral and structural studies of 4‐aminobenzenesulfonamide (sulfanilamide)‐d0, ‐d4, and ‐15N, as well as their azanions: Combined DFT B3LYP/experimental approach

AbstractThe infrared (IR) spectra of sulfanilamide 1 and of its azanion (counter ion Na+) 2 have been measured in dimethyl sulfoxide (DMSO) solutions. The density functional theory (DFT) B3LYP 6‐31++G(d,p) computations performed adequately describe the experimental spectroscopic data, including the corresponding frequency isotopic shifts. In agreement between theory and experiment, the conversion of sulfanilamide 1 into azanion 2 results in strong frequency decreases of the asymmetrical and symmetrical vibrations of the SO2 group: predicted 122 cm−1, measured 140 cm−1 in solution (total values), as well as in other essential IR spectral changes. According to the computations, the strongest changes in the steric structure take place at and next to the azanionic center. The new (azanionic) charge is distributed, as follows: 0.08e−, 0.23e−, and 0.12e− are delocalized over the amino, phenylene, and sulfonic groups, respectively, and 0.57e− of it remain localized at the azanionic center. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007

Inhibition and partial reactions of Na,K‐ATPase studied by fourier transform infrared difference spectroscopy

Reaction-induced infrared (IR) difference spectroscopy with caged ATP and Na,K-ATPase allows us to differentiate unambiguously between phosphorylated and unphosphorylated states of the enzyme as well as of its ouabain complex. The IR spectral changes upon phosphoenzyme formation are characterized and interpreted. Our results show clearly that high Na(+) concentrations prevent the binding of ouabain with high affinity, which is consistent with the results of a corresponding kinetic study employing spectrofluorimetry and calorimetric titrations. This unexpected antagonism leading to low ouabain affinity is assumed related to a conformation of the protein, induced by low affinity binding of the third Na(+) ion. We thus conclude that not the free enzyme but a phosphorylated state of the reaction cycle preferentially binds ouabain and leads to the loss of hydrolytic activity.

Premelting Behavior of a Langmuir−Blodgett Film of Dioctadecyldimethylammonium-Au(dmit)2 Salt

Premelting behavior of a Langmuir-Blodgett (LB) film of dioctadecyldimethylammonium-Au(dmit)2 (2C 1 8 -Au(dmit) 2 ) salt has been studied by means of infrared (IR) transmission spectroscopy. Two bands due to the CH 2 antisymmetric stretching (v a s (CH 2 )) and symmetric stretching (v s (CH 2 )) modes have been used to monitor the conformation and orientation of a hydrocarbon chain in the 2C 1 8 -Au(dmit) 2 LB film, and a band due to the C=S stretching mode has been employed to investigate the aggregation state of Au(dmit) 2 chromophores. The global phase mapping method in the generalized two-dimensional correlation spectroscopy (global 2D phase mapping method) has been used for examining the overlapping, shifting, and broadening of absorption components in the v s (CH 2 ) band (2841-2856 cm - 1 region). Temperature-dependent IR spectral changes have revealed that there are, at least, four different ordered stages in the LB film below the order-disorder transition between 105 and 110 °C. (i) In the temperature range of 30-50 °C, the orientation and conformation of hydrocarbon chain and the aggregation state of Au(dmit) 2 chromophores do not change appreciably, in which the hydrocarbon chain contains the disordered component to some extent, compared to the most highly ordered state of the hydrocarbon chain at 60 °C. (ii) From 50 to 60 °C, the new aggregation state of Au(dmit) 2 chromophores appears, while the hydrocarbon chain changes drastically to the specific orientation where the transition moment of the v s (CH 2 ) mode tends to be aligned parallel to the substrate surface, with the trans forms increasing. (iii) From 60 to 80 °C, the aggregation state of Au(dmit) 2 chromophores observed at 30 °C is almost completely converted into the new aggregation state, while the hydrocarbon chain keeps the specific orientation on average, with the gauche forms increasing. (iv) From 80 to 105 °C, the new aggregation state of Au(dmit) 2 chromophores remains almost unchanged until the order-disorder transition, while the hydrocarbon chain changes to the disordered state, with the gauche forms increasing. The above results have indicated that the heat treatments after the film deposition can be used for controlling the structure of the 2C 1 8 -Au(dmit) 2 LB film.

ChemInform Abstract: Two‐Dimensional Infrared and Near‐Infrared Correlation Spectroscopy: Applications to Studies of Temperature‐Dependent Spectral Variations of Self‐Associated Molecules

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Two-Dimensional Infrared and Near-Infrared Correlation Spectroscopy: Applications to Studies of Temperature-Dependent Spectral Variations of Self-Associated Molecules

This paper demonstrates the potential of generalized two-dimensional (2D) Fourier transform (FT) infrared (IR) and near-infrared (NIR) correlation spectroscopy in the studies of temperature-dependent spectral variations of self-associated molecules. Three examples of the 2D correlation analysis are discussed in this paper. The first two are concerned with the temperature-dependent IR and NIR spectral changes of N-methylacetamide (NMA) in the pure liquid state. The 2D IR correlation approach revealed that almost all the peaks of NMA in the 3400–1100-cm−1 region consist of two to four separate bands. For example, the amide I band contains contributions from at least four distinct bands at 1685, 1665, 1650, and 1635 cm−1. The analysis of the asynchronous 2D IR spectrum in the amide I region showed that the sequence of spectral intensity change in the ascending order of temperature was given by 1635<1650<1665<1685 cm−1. These bands at 1635, 1650, 1665, and 1685 cm−1 were assigned to the amide I modes of chain oligomers of various sizes and dimer of NMA; the longer the chain, the lower the frequency. The closeup view of 2D NIR correlation spectra of NMA obtained at narrow spectral and temperature windows enabled us to propose not only band assignments in the 6800–6050-cm−1 region but also a detailed mechanistic picture of the thermally induced dissociation of NMA for each temperature range. We also applied the generalized 2D correlation approach to the analysis of a set of FT NIR spectra of oleyl alcohol under temperature variations. The 2D NIR analysis enhanced the spectral resolution and simplified the spectra with overlapped bands. For example, it was found that a band at 7090 cm−1 arising from the first overtone of an OH stretching mode of the monomeric alcohol consists of two bands due to the rotational isomerism of the free OH group. An intriguing possibility of correlating various overtone and fundamental bands to establish unambiguous assignments was also suggested from the 2D NIR study on oleyl alcohol.

Vibrational spectroscopic study on low-molecular-weight polyoxymethylene diacetate

Infra-red and Raman spectra of low-molecular-weight polyoxymethylene diacetates are investigated and compared with those of the extended- and folded-chain crystals of high-molecular weight trigonal polyoxymethylene. Some bands assignable to the A 2 symmetry species shift towards the high-frequency side, as was found in the folded-chain crystal. The infra-red spectral changes for the extended-chain crystal, folded-chain crystal and low-molecular-weight polyoxymethylene diacetates that occur on mechanical deformation and melt crystallization are also discussed. A minor shift of Raman bands of the low-molecular-weight polyoxymethylene diacetates was also found and discussed.

Effects of the degree of polymerization of oligosaccharides on the properties of ground mixtures.

X-Ray analysis, differential thermal analysis (DTA) and infrared (IR) spectroscopy have been used to investigate the influence of the degree of polymerization of oligosaccharides on the dispersion state and the interaction of drugs (aspirin and methylparaben) during grinding with oligosaccharides. When a drug was ground with maltoheptaose or maltopentaose, the crystalline peaks of the drug in the powder X-ray diffraction pattern and the heat of fusion of the drug on DTA disappeared, and some IR spectral changes were observed. In the case of the ground mixture with maltotriose, an amorphous state of the drug was observed from the powder X-ray diffraction and DTA results, but there was no change in the IR spectrum. In the case of the ground mixture with maltose, the crystallinity of the drug was scarcely altered by the grinding.These results indicate that in the ground mixtures with maltopentaose and maltoheptaose, drug molecules were dispersed monomolecularly in the hydrogen-bonded networks of oligosaccharides. On the other hand, in the maltotriose system, although the drug was in an amorphous state, the drug was not in a molecular dispersion due to the low degree of polymerization of maltotriose.

On the structures of carbon monoxidevinylchloride copolymers

Carbon monoxide-vinylchloride copolymers have been obtained by various methods. Recently, Ratti et al have reported that the copolymer obtained in bulk at 50° using bis-(4-tertbutylcyclohexyl)-peroxydicarbonate has an acid chloride structure, there being a rearrangement involving 1–2-shift of chlorine atoms. In the present paper, it is reported that the copolymer obtained by procedures of the present author probably contains the a-ketonic group, in view of the infra-red spectral changes produced by treatments in solvents and by reduction with sodium borohydride.

Photothermal degradation of copolymers of methyl methacrylate and n-butyl acrylate

The photothermal degradation of copolymers of methyl methacrylate (MMA) and n-butyl acrylate ( n-BuA) covering the whole composition range has been studied at 165°. The gaseous products, which are relatively minor, are hydrogen, carbon monoxide and methane. The liquid products are predominantly MMA, with n-BuA, n-butanol and n-butyraldehyde as minor products. Infra-red spectral changes in the residue were attributed to lactone formation and associated with butanol formation as in the purely thermal reaction The “cold ring” or chain fragment fraction becomes increasingly more abundant as the n-BuA content of the copolymer is increased. All the products and principal features of the reaction are explained in terms of a radical process which is initiated by scission of pendant acrylate units and is propagated by a combination of depropagation and intra- and intermolecular transfer processes, the relative importance of which depends upon copolymer composition. Differences from the thermal reaction and the corresponding reaction in copolymers of methyl methacrylate and methyl acrylate are discussed.

An infra-red study of the crystallization of poly(vinyl chloride)

We have studied infra-red spectral changes in the 3,000–800 cm −1 region on crystallizing poly(vinyl chloride) specimens. The optical densities of the 1,428, 1,333, 1,254, 1,226 and 955 cm −1 bands increase linearly with increasing specific gravity or crystallinity. The 1,434 cm −1 band is assigned to both the δ (CH 2) mode of disordered, and the δ (CH 2) i(A 1) mode of the syndiotactic, portions of the polymer molecule. The crystallization-sensitive band at 1,428 cm −1 is ascribed to interactions in the crystalline regions of the polymer. The 1,226 cm −1 band may be assigned to the γw (CH 2) i(B 2) or γw (CH) i(B 2) modes. Though the infra-red dichroism is questionable, the 955 cm −1 band may be due to the γr (CH 2) i(B 1) mode in the crystalline regions. The shoulder at 965 cm −1 is assignable to the γr (CH 2) mode of amorphous regions.

Infra-Red Spectral Changes Accompanying Methylation of Brown Coals

Infra-Red Spectral Changes Accompanying Methylation of Brown Coals

A proposed interpretation of infra-red spectral changes occurring upon the interaction of polynucleotides.

IT has been found that the sodium salts of polyadenylic and polyuridylic acids interact1–4 with formation of a two-stranded helix1 with a structure very similar to deoxyribonucleic acid. More recently it was observed that the infra-red spectrum5 of the mixture of these two acids showed the following marked changes from the summation of the curves of the components : a 39 per cent reduction in intensity of the 1,627 cm.−1 band and a 7 cm.−1 shift to higher frequency ; a decrease in peak height (because of strong overlap the band was not integrated) and an 11 cm.−1 shift to higher frequency of the 1,661 cm.−1 band. The interaction of the sodium salts of polycytidylic and polyinosinic acids6 has now been observed in the infra-red7 with the following result : a marked decrease in intensity of the 1,651 cm.−1 peak of the sodium salt of polycytidylic acid (the intensities have not yet been put on a quantitative basis) and a 19 cm.−1 shift to higher frequency of the 1,678 cm.−1 peak of the sodium salt of polyinosinic acid.