SEARCH · PubMed Health

Results for “Spectroscopy, Fourier Transform Infrared”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources

PubMed1995

Fourier transform infrared spectroscopy indicates a major conformational rearrangement in the activation of rhodopsin.

The study of the structural differences between rhodopsin and its active form (metarhodopsin II) has been carried out by means of deconvolution analysis of infrared spectra. Deconvolution techniques allow the direct identification of the spectral changes that have occurred, which results in a significantly different view of the conformational changes occurring after activation of the receptor as compared with previous difference spectroscopy analysis. Thus, a number of changes in the bands assigned to solvent-exposed domains of the receptor are detected, indicating significant decreases in extended (beta) sequences and in reverse turns, and increases in irregular/aperiodic sequences and in helices with a non-alpha geometry, whereas there is no decrease in alpha-helices. In addition to secondary structure conversions, qualitative alterations within a given secondary structure type are detected. These are seen to occur in both reverse turns and helices. The nature of this spectral change is of great importance, since a clear alteration in the helices bundle core is detected. All these changes indicate that the rhodopsin --> metarhodopsin II transition involves not a minor but a major conformational rearrangement, reconciling the infrared data with the energetics of the activation process.

Analysis of Variance↗

PubMed2005

Classification of modified starches by fourier transform infrared spectroscopy using support vector machines.

The aim of this study was to compare the performance of different supervised discrimination methods based on IR data for the classification of starches according to the type of chemical modification undergone. The goal of the supervised classification methods is to develop classification rules. Representative samples of each group (known beforehand) were available, from which the relevant characteristics (chemical modification) were known. On the basis of a training data set, classification rules are determined, which can then be applied to classify new (unknown) samples.

Spectroscopy, Fourier Transform Infrared↗

PubMed2000

[Fourier transform infrared spectroscopy, molecular biologic methods and antimyocotic susceptibility patterns for identification and differentiation of cryptococcus species].

Molecular biological methods as well as the FTIR method allows the rapid, reliable and reproducible determination and identification of Cryptococcus species from human, veterinary and environmental origin and their serovars. The results obtained by FTIR could be verified by the molecular methods. In addition, with the PCR and FTIR fingerprinting methods it is possible to distinctly group the serovars and differentiate the different Cryptococcus strains.

Animals↗

PubMed1995

Fourier transform infrared spectroscopy investigations of protein structure.

Infrared spectroscopy can provide insight into protein structure. This technique is sensitive to the backbone amide arrangement of peptide and protein molecules. In many cases, complementary as well as more expansive information is obtained as opposed to information obtained by other methods that examine the molecule's environmental surroundings, require molecular probes, or perhaps cannot investigate the molecule in its native environment. The foundation for spectroscopic differences between the various secondary structures arises not only from geometrical differences and hydrogen bond variations but also transition dipole coupling between neighboring oscillators. Theoretical predictions of protein spectra have been made using normal mode analysis and combined with experimental data. At present the amide I band has provided the most insight into secondary structure. Even more convincing results are obtained when both H2O and D2O are used as solvents. Recent advances in computerized technology and mathematical techniques have expanded the potential contributions of infrared spectroscopy in the area of protein structural determination. However, the limitations of resolution enhancement and curve-fitting techniques must be taken into consideration. The parameters must be carefully and optimally chosen and evaluated on a case-by-case basis. The subjectivity of these techniques makes a thorough understanding of the algorithms necessary, especially those commercially available. Infrared spectroscopy continues to provide insight into protein and peptide structures under biologically relevant conditions that enable the structure-function relationships for such molecules to be better understood.

Amides↗

PubMed2002

The potential role of Fourier transform infrared spectroscopy and imaging in cancer diagnosis incorporating complex mathematical methods.

Infrared spectroscopy and imaging technology can provide new diagnostic capabilities for cancer research applications and to physicians directly involved in patient treatment. A methodology that permits the phenotypical description of cells and tissues is introduced, as well as a variety of new evaluation techniques that allow researchers and physicians to evaluate the infrared data at different levels of sophistication. The detection of cell alterations in the case of Chronic Lymphocytic Leukemia (CLL) demonstrates the capability of infrared spectroscopy to identify and stage this type of cancer, providing new prospects for diagnosis and treatment. The pathological study of oral tissue affected by Squamous Cell Carcinoma (SCC) illustrates the potential of Infrared Spectroscopy and Imaging for tissue diagnosis and cancer staging based in altered cell biochemistry, without using stains or any other marker technology. An example of combined fluid, cell and tissue analysis of thyroid cancers based on infrared technology is introduced to demonstrate the possibility of earlier detection of gland abnormalities and biochemical alterations in cell extracts using fine needle aspirates. Simple statistical techniques such as bivariate histogram analysis can distinguish between normal and altered cells and tissues when applied to infrared spectra and images. More complex mathematical techniques such as Principal Component Analysis (PCA) or Artificial Neural Networks (ANN) provide additional evaluation capabilities that can relate spectra of an unknown sample to an infrared reference database of known cell states. It is documented how this new infrared technology could enhance the diagnoses, treatment decisions and prognoses of patients in the field of cancer medicine.

Apoptosis↗

PubMed2006

Detection of albumin unfolding preceding proteolysis using Fourier transform infrared spectroscopy and chemometric data analysis.

The hydrolysis of bovine serum albumin with protease K at 60 degrees C has been studied by means of infrared spectroscopy. Two-dimensional correlation spectroscopy (2DCoS) has been used to study spectral changes in the reaction. The use of the multivariate curve resolution-alternating least-squares method applied to infrared measurements allowed the recovery of pure infrared spectra and concentration profiles of the different species involved in the reaction. Special attention was paid to the careful inspection of residuals again using 2DCoS. In this way, a heat-induced unfolding step previous to protein hydrolysis was identified. The infrared spectra of the intermediate species showed a more disordered structure than native albumin, the decrease in alpha-helix conformation being especially noticeable. The formation of beta-sheet aggregates due to heating was detected too.

Animals↗

PubMed2000

Monitoring of phospholipid monolayer hydrolysis by phospholipase A2 by use of polarization-modulated Fourier transform infrared spectroscopy.

Polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) was used to follow the hydrolysis of phospholipid monolayers at the air-water interface by phospholipase A2 (PLA2). The decrease in the intensity of the nuC=O ester band of dipalmitoylphosphatidylcholine at 1733 cm(-1) and the appearance of two new infrared bands in the 1530-1580 cm(-1) region allowed to monitor phospholipid hydrolysis by PLA2. Indeed, the decrease in the intensity of the band at 1733 cm(-1) was attributed to the enzymatic hydrolysis of the acyl ester linkage of the sn-2 fatty acid on the glycerol backbone whereas the doublet appearing at 1537 and 1575 cm(-1) was attributed to the nu(a) COO- vibration of the newly formed calcium-palmitate. The presence of this band as a doublet indicates the formation of a crystalline-like calcium-palmitate monolayer. This observation supports our previously postulated mechanism for the formation of PLA2 domains at the air-water interface. Definitive assignment of the infrared bands has been possible by measuring PM-IRRAS spectra of the individual hydrolysis products (palmitic acid and lysopalmitoylphosphatidylcholine) as well as of 1-caproyl-2-palmitoyl-phosphatidylcholine and 1-palmitoyl-2-caproylphosphatidylcholine monolayers before and after hydrolysis by PLA2.

Hydrolysis↗

PubMed1997

Effect of sampling procedure and strain variation in Listeria monocytogenes on the discrimination of species in the genus Listeria by Fourier transform infrared spectroscopy and canonical variates analysis.

The ability to discriminate successfully among cultures of all species of the Listeria genus by infrared spectroscopy in combination with canonical variate analysis was confirmed. The robustness of the method was demonstrated by showing that the separation of L. monocytogenes and L. grayi was hardly affected by variations in broth medium, incubation temperature, incubation time and cell washing procedure. Discrimination among 24 strains of L. monocytogenes according to serotype allowed two groups to be recognised, one comprising serotypes 4 and 4b and the other containing serotypes 1, 1/2b and 1/2c. When strain variation was included in the species discrimination model, the classification of all the L. monocytogenes strains was virtually 100% correct.

Culture Media↗

PubMed1995

Tertiary stability of native and methionine-80 modified cytochrome c detected by proton-deuterium exchange using on-line Fourier transform infrared spectroscopy.

The stability of the tertiary structure of cytochrome c and of a methionine-80 chemically modified form of this protein has been investigated by monitoring on-line the exchange of amide protons with deuterons using infrared spectroscopy. The modified protein has a structural stabilization energy of approximately 50% of that of native cytochrome c, whereas the secondary structure is not affected by the modification. In the modified protein the fraction of slow exchanging amides is smaller compared to that in the native protein, and the exchange rate constants are found to be 2-3 times larger for the slow (half-life of 5.5 h) and intermediate (half-life of 4.1 min) exchanging fraction of amides. The exchange rate of a fast exchanging fraction of amides (half-life smaller than 1 min), most likely surface exposed amides, is not influenced by tertiary destabilization of the protein. The results in aqueous solution agree well with data obtained by monitoring the amide-proton exchange using 1H-nuclear magnetic resonance. In films, using attenuated total reflection infrared techniques, this difference in tertiary stability between modified and native cytochrome c could also be demonstrated. The various advantages and complications of this approach are discussed in detail.

Amides↗

PubMed2004

Fourier transform infrared spectroscopy as a new tool to determine rosmarinic acid in situ.

A new procedure has been developed for the in situ FT-IR determination of rosmarinic acid (RA) in suspension cultures of Lavandula officinalis. The method involves sample preparation on ZnSe crystals or microplates from silicon, and measuring absorbance spectra between 4000 and 700 cm(-1). First derivative spectra were analysed after normalisation using partial least square (PLS) algorithm. The correlation between spectral analysis and HPLC measurements of cell extracts shows that the FT-IR procedure is suitable for qualitative and quantitative analyses of RA in cell suspension cultures.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1996

Determination of molecular order in supported lipid membranes by internal reflection Fourier transform infrared spectroscopy.

When polarized internal reflection infrared spectroscopy is used to determine molecular order in supported lipid membranes, the results are critically dependent on the accuracy of assumptions made about the evanescent electric field amplitudes in the membrane. In this work, we examine several expressions used for calculating evanescent electric field amplitudes in supported lipid monolayers and bilayers, and test their validity by measuring the infrared dichroism of poly-gamma-benzyl-L-glutamate and poly-beta-benzyl-L-aspartate under conditions in which their molecular order is known. Our results indicate that treating such systems as a simple single interface between two semi-infinite bulk phases is more accurate than the commonly employed thin-film approximation. This implies that earlier conclusions about molecular order in supported lipid membranes may require substantial revision.

Liposomes↗

PubMed2006

[Study on interaction of anionic surfactant SDS and bovine serum albumin by fourier transform infrared spectroscopy].

FTIR spectroscopy was applied to investigate the interaction of anionic surfactant Sodium Dodecyl Sulfate (SDS) and Bovine Serum Albumin (BSA). Amide band I of BSA was analyzed to obtain the change in secondary structure of BSA when different concentration of SDS was added and during different interaction period. In short interaction period and at low concentration of SDS, the alpha-helixes increased and the random coil decreased. In long interaction period or at high concentration of SDS, SDS unfolded the protein by decreasing the alpha-helix structure and increasing the random coil.

Animals↗

PubMed2001

Process control of apple winemaking by low-resolution gas-phase Fourier-transform infrared spectroscopy.

Four apple wine fermentation processes have been observed by means of direct-inlet gas-phase FTIR spectroscopy. The apple juice concentrates were each fermented by two species of Saccharomyces cerevisiae starters, and the experiment was repeated. The development of the concentrations of 1-propanol, 4-methylpyridine, acetaldehyde, acetic acid, and ethyl acetate was monitored. Two different sampling methods were used--static headspace and direct injection of the must. The performance of the FTIR method is limited by the high ethanol concentration. It can be mathematically proven that the amount of sample can be selected so that any distortion due to ethanol is minimized. Headspace GC-MS was used for preliminary compound identification.

1-Propanol↗

PubMed2001

Structural changes of human serum albumin immobilized on chromatographic supports: a high-performance liquid chromatography and Fourier-transform infrared spectroscopy study.

Chiral stationary phases obtained by immobilization of HSA on [C8] and [C18] reversed-phases and on poly(1-vinylimidazole)-coated silica were tested to resolve DL-tryptophan, N-benzoyl-DL-phenylalanine, RS-oxazepam and RS-warfarin racemic mixtures. Parameters of enantioselectivity measured in HPLC are correlated to structural and solvation states for adsorbed HSA, evaluated by FTIR spectroscopy. HSA immobilized on [PVI]-anion-exchangers is highly selective. HSA molecules are not self-associated, only unfolded for a small hydrophobic helix. The HSA-coated reversed-phases have a lower selectivity. Unfolding is larger but the indole-benzodiazepine chiral site is preserved and remains accessible.

Albumins↗

PubMed1994

Quantitative analysis of residual detergent in proteoliposomes by Fourier transform infrared spectroscopy.

An infrared spectroscopic method has been developed to quantify the residual amount of detergent present in membranes, e.g., after reconstitution of a membrane protein in phospholipids. A detergent-specific band is selected in the ir spectrum and the intensity is ratioed against a phospholipid-specific band (around 1235 cm-1, vas (P = O)). This ratio shows a linear relation with the molar ratio of detergent of phospholipid, down to as low as 1 to 10. The new method is illustrated in two case studies, viz., tris(hydroxyethyl)ammonium cholate in Na+/K(+)-ATPase proteoliposomes and n-dodecyl-beta-D-maltoside in rhodopsin proteoliposomes.

Animals↗

PubMed2003

Effects of ELF magnetic field on membrane protein structure of living HeLa cells studied by Fourier transform infrared spectroscopy.

The effects of exposure to a 50 Hz magnetic field (maximum of 41.7 to 43.6 mT) on the membrane protein structures of living HeLa cells were studied using attenuated total reflection infrared spectroscopy. One min of such exposure shifted peak absorbance of the amide I band to a smaller wave number, reduced peak absorbance of the amide II band, and increased absorbance at around 1600 cm(-1). These results suggest that exposure to the ELF magnetic field has reversible effects on the N-H inplane bending and C-N stretching vibrations of peptide linkages, and changes the secondary structures of alpha-helix and beta-sheet in cell membrane proteins.

Albumins↗

PubMed1998

Room-temperature vibrational difference spectrum for S2QB-/S1QB of photosystem II determined by time-resolved Fourier transform infrared spectroscopy.

Time-resolved FTIR spectroscopy has been used to kinetically characterize the vibrational properties of intact photosystem II-enriched membrane samples undergoing the S1QB-to-S2QB- transition at room temperature. To optimize the experimental conditions for the FTIR measurements, oxygen polarographic and variable chlorophyll a fluorescence measurements were used to define the decay of S2 and QA-, respectively. The flash-induced S2QB-/S1QB difference spectra were measured at a temporal resolution of 4.44 s and a spectral resolution of 4 cm-1. An intense positive band is observed at 1480 cm-1 in the difference spectrum and shows a slow decay with a half time of approximately 13 s. Based on its decay kinetics and analogy to the infrared absorption of QA- of photosystem II and QB- in bacterial reaction centers, we conclude that the 1480 cm-1 band arises from QB- of PSII and tentatively assign it to the upsilon(CO) mode of the semiquinone anion QB-. The infrared spectral features attributed to the S1-to-S2 transition of the Mn cluster at room temperature show striking similarity to the S2/S1 difference spectrum measured at cryogenic temperatures (Noguchi, T., Ono, T.-A., and Inoue, Y. (1995) Biochim. Biophys. Acta 1228, 189-200).

Chloroplasts↗

PubMed2007

Treatment of olive mill waste-water by aerobic biodegradation: an analytical study using gel permeation chromatography, ultraviolet-visible and Fourier transform infrared spectroscopy.

Liquid waste from olive oil mills was digested following inoculation with soil microorganisms and fractionated through various grades of gel. The fractionation showed the range of sizes of the molecules in the waste. In addition, the disappearance of the low molecular weight fraction, which is retained by the gel, and the increase of the high molecular weight fraction, which is excluded by the gel, during the last stages of the microbial treatment, indicates polymerisation of the low-molecular-weight subunits. Characterization of the fractions by UV-visible and FTIR spectroscopy confirmed the increase in their degree of polymerisation during the treatment. This is paralleled by a reduction in the amount of aliphatic components and a concomitant increase in aromatic structures.

Aerobiosis↗