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PubMed1992

Structural analysis of pigeon lens crystallins by near-infrared Fourier transform Raman spectroscopy.

Crystallins from pigeon eye lenses were isolated and purified by gel-permeation and anion-exchange chromatographies and characterized by gel electrophoresis, amino acid analysis and Raman spectroscopy. alpha- and beta-Crystallins could be obtained in relatively pure forms by single-step size-exclusion chromatography whereas an extra step of ion-exchange chromatography was needed for the separation of delta crystallin from the beta-crystallin fraction. In contrast to most characterized vertebrate species, a large amount of glycogen is eluted as a high molecular form in the first peak of gel filtration column. Structural analyses of total crude soluble proteins and purified alpha-, beta- and delta-crystallin fractions were made with respect to their amino acid compositions and characteristic near-IR Fourier-transform Raman spectra. The results indicate that the major secondary structures of alpha- and beta-crystallins are mainly anti-parallel beta-pleated sheet in nature as judged by the Raman signals at 1242 (amide III) and 1669-1670 cm-1 (amide I) whereas delta-crystallin consists of a significant content of alpha-helices as evidenced by the Raman signal at 1657-1660 cm-1 (amide I). The low intensity of S-S disulfide stretching vibration at 508-510 cm-1 coupled with the presence of S-H stretching at 2560-2580 cm-1 for alpha-, beta- and delta-crystallin pointed to the fact that sulfhydryl groups in most crystallins are resistant to air oxidation during the process of homogenization and protein extraction. It is also found that the relative Raman signal intensities of Tyr, Phe, and Trp residues in purified crystallins correlate very well with the data obtained from amino acid analysis. Especially noteworthy is the demonstrated usefulness of applying Raman techniques in the detection of the microenvironments of the aromatic amino acids such as Tyr and Trp in the native crystallins, which may prove useful in the study of contribution of these aromatic residues to crystallin packing and stability.

Amino Acids↗

PubMed1991

Differential pathlength factor for diffuse photon scattering through tissue by a pulse-response method.

Although near-infrared (NIR) spectroscopy may one day provide a noninvasive measurement of oxidative metabolism in tissue, the method cannot be fully quantitative until the mean pathlength traveled by photons between reference and output detectors (i.e, optrodes) is known. In NIR spectroscopy, photons are transported primarily by diffuse scattering, and their mean pathlength can be expressed by a differential path factor (DPF) whose value is greater than the interoptrode distance. Beginning with a P1 diffusion approximation of the Boltzmann equation, one-dimensional photon currents originating from plane, line, and point photon sources were analyzed. DPF was formulated from the attenuation of light intensity generated by constant sources, and an equation for the mean time of flight of photons between reference and output optrodes, delta tau, was derived for arbitrarily pulsed sources. The results indicate that (1) the attenuation of light in tissue does not, in general, vary with interoptrode distance in the manner predicted by Beer's law; (2) the relationship between DPF and interoptrode distance is nonlinear and geometry-dependent; and (3) in spite of these nonidealities, DPF is equal to the product of delta tau and the speed of light.

Metabolism↗

PubMedDate not supplied

Cerebrocortical oxygenation and ventilatory response during sustained hypoxia.

Cerebrocortical oxygenation was monitored in 8 healthy adults during exposure to sustained isocapnic hypoxia. Subjects were maintained at an arterial oxygen saturation (SaO2) of 80% for 12 min with a rebreathing circuit while cerebrocortical oxygenation was assessed non-invasively using near-infrared (NIR) spectroscopy to measure changes in the oxidation state of cytochrome a,a3 (Cyt a,a3) and changes in cortical blood volume (tBV). During sustained hypoxia, subjects demonstrated a biphasic ventilatory response. The mean minute ventilation (VE) peak response was 255% of baseline at an average of 3.4 +/- 0.5 min (mean +/- SE) after the initiation of hypoxia. A subsequent significant attenuation of VE to 163% (P less than 0.05) of baseline occurred after an additional 8.6 min. NIR monitoring revealed a significant (P less than 0.05) decrease in oxidized Cyt a,a3 as well as a significant (P less than 0.05) increase in tissue blood volume (tBV) at the time of peak VE. Both Cyt a,a3 and tBV remained stable during the remainder of the hypoxic period, despite attenuation of VE during sustained hypoxia. The data suggest that cerebrocortical oxygenation and blood flow remain constant when the ventilatory attenuation is observed during sustained hypoxia.

Blood Volume↗

PubMed1992

Fourier transform resonance Raman spectroscopy of phytochrome.

The Pr and Pfr forms of phytochrome in H2O and D2O have been studied by Fourier transform resonance Raman spectroscopy with near-infrared excitation (1064 nm). It is demonstrated that this technique is a powerful method for analyzing the chromophore structures of photosensitive pigments. The high spectral quality allows discussion of vibrational assignments based on an empirical approach using previously published data obtained from model compounds. The reduction in intensity of a high-frequency band assigned to the ring-C/D methine bridge vibration is an indication for the non-coplanarity of the ring D in Pfr. The high intensity of a C-H out-of-plane vibration also supports this hypothesis. In Pr, a broad peak at approximately 1100 cm-1 is assigned to an out-of-plane vibration of a strongly hydrogen-bonded pyrrole C=NH+ group. It is missing in Pfr, suggesting deprotonation of the corresponding ring during the transformation from Pr to Pfr.

Chemical Phenomena↗

PubMed1991

Primary donor structure and interactions in bacterial reaction centers from near-infrared Fourier transform resonance Raman spectroscopy.

Preresonance Raman and resonance Raman spectra of the primary donor (P) from reaction centers of the Rhodobacter (Rb.) sphaeroides R26 carotenoidless strain in the P and P+ states, respectively, were obtained at room temperature with 1064-nm excitation and a Fourier transform spectrometer. These spectra clearly indicate that the chromophore modes are observable over those of the protein with no signs of interference below 1800 cm-1. The chromophore modes are dominated by those of the bacteriochlorophylls (BChl a), and it is estimated that, in the P state, ca. 65% of the Raman intensity of the BChl a modes arises from the primary donor. This permits the direct observation of a vibrational spectrum of the primary donor at preresonance with the excitonic 865-nm band. The Raman spectrum of oxidized reaction centers in the presence of ferricyanide clearly exhibits bands arising from a BChl a+ species. The magnitude of the frequency shift of a keto carbonyl of neutral P from 1691 to 1717 cm-1 upon P+ formation strongly suggests that one BChl molecule in P+ carries nearly the full +1 charge. Our results indicate that the unpaired electron in P.+ does not share a molecular orbital common to the two components of the dimer on the time scale of the resonance Raman effect (ca. 10(-13) s).

Fourier Analysis↗

PubMed2026

Dissecting the genetics of forage quality traits in soft red winter wheat in the U.S. southeast region.

Winter wheat plays a viable role in agriculture, not only as a primary grain crop but also as a valuable forage source that bridges fall-spring forage gaps in many regions, including the southeastern (SE) U.S. Despite its nutritive potential, genetic basis of forage-quality traits remains insufficiently understood, limiting breeding efforts for dual-purpose cultivars. This study aimed to dissect the genetic architecture of forage quality in 182 soft red winter wheat (SRWW) genotypes adapted to the SE U.S. using genome-wide association study (GWAS). Field experiments were carried out in randomized complete block design across three Georgia locations over two growing seasons (2023-2025), with forage sampled at the end of tillering and evaluated using near-infrared reflectance spectroscopy. Significant phenotypic variation was observed for dry matter (DM), crude protein (CP), acid and neutral detergent fiber (ADF, NDF), acid detergent lignin (ADL), total digestible nutrients (TDN), sugars (SUG), and relative forage quality (RFQ). Heritability estimates ranged from low-to-moderate in combined environments and from low-to-high within individual locations. Correlation analysis revealed strong positive associations among fiber-related traits and negative associations with TDN, RFQ, and SUG, while CP declined with increasing fiber. Genome-wide association analysis identified 282 significant marker-trait associations (P < 1×10-4) across 19 chromosomes, which were consolidated into 121 QTLs, including 27 major-effect QTLs. Three QTLs QRfq.uga-3B.1, QRfq.uga-3B.2 (RFQ) and QDm/Sug.uga-7A (DM, SUG) were stable across locations while QAdf/Adl.uga-2A (ADF, ADL) and QDm/Sug.uga-7A (DM, SUG) indicated multi-trait control. Notably, 25 of the 27 major QTLs were putatively novel, highlighting substantial untapped allelic diversity for forage-quality improvement in SE SRWW. Favorable allele accumulation resulted in an overall improvement in forage quality, increasing desirable nutritive traits (DM, RFQ, SUG, CP) while reducing undesirable traits (ADF, ADL). Candidate gene analysis linked six major QTLs with genes implicated in abiotic stress response, plant development, and metabolic regulation, supporting their functional relevance in forage-quality determination. Incorporating these loci into breeding programs provides a robust genetic framework for marker-assisted selection, enabling the development of dual-purpose wheat cultivars with enhanced forage quality, thereby strengthening wheat's utility as a reliable forage resource during periods of seasonal feed scarcity in SE production systems.

GWAS↗

PubMed1992

Noninvasive glucose monitoring in diabetic patients: a preliminary evaluation.

Noninvasive monitoring of blood/tissue glucose concentrations has been successfully accomplished in individual diabetic subjects by using near-infrared (NIR) spectroscopy coupled with chemometric methods. Three different spectrometer configurations were tested: a) a Fourier-transform infrared spectrometer with an indium antimonide detector; b) a grating monochromator equipped with a silicon (Si) array detector, without fiber optics; and c) a grating monochromator equipped with an Si detector, with fiber-optic sampling. NIR spectra were obtained from diabetic subjects by transmission through the finger during a meal-tolerance test. The maximum range of observed plasma glucose concentrations obtained from the blood samples was 2.5-27 mmol/L. The NIR spectra were processed by using the chemometric multivariate calibration methods of partial least squares and principal component regression. The best calibration yielded a cross-validated average absolute error in glucose concentration of 1.1 mmol/L. This predictive ability suggests that noninvasive glucose determinations by NIR/chemometrics is a viable analytical method.

Blood Glucose↗

PubMed1990

Near-infrared optical responses in feline brain and skeletal muscle tissues during respiratory acid-base imbalance.

The effects of hyper- and hypocapnia on oxidative metabolism were evaluated by near-infrared (NIR) multiwavelength spectroscopy in intact brain and skeletal muscle tissues of the anesthetized cat. A 3-wavelength NIR algorithm was used to monitor cytochrome a,a3 oxidation state, regional blood volume, and tissue oxyhemoglobin and O2 stores simultaneously in brain and muscle in ventilated animals. Incremental hypercapnia was produced in 10 cats by raising arterial pCO2 from 27.0 +/- 1.3 to 95.1 +/- 1.9 mmHg with inspired CO2. Hypercapnia produced progressive increases in cerebral HbO2, blood volume, and cytochrome a,a3 oxidation state (P less than 0.01). In contrast, CO2 simultaneously decreased all 3 NIR parameters in intact hindlimb muscles (P less than 0.01). Blood volume changes during hypercapnia correlated with changes in blood flow measured qualitatively by intravascular injections of indocyanine green dye. Hypocapnia produced by hyperventilation in 8 cats lowered paCO2 from 28.5 +/- 0.4 to 13.5 +/- 0.5 mmHg. Hypocapnia decreased cerebral HbO2, blood volume, and cytochrome a,a3 redox level (P less than 0.05), but NIR changes were not seen in skeletal muscle. These experiments demonstrate preferential distribution of oxygen to brain during hypercapnia and the ability of NIR spectroscopy to assess regional oxygenation in multiple tissues non-invasively.

Acid-Base Imbalance↗

PubMed1992

Noninvasive methods for estimating in vivo oxygenation.

Clinical signs of hypoxia and hyperoxia are nonspecific and unreliable, yet both are potentially injurious. Noninvasive methods of oxygen assessment fill the gap between clinical observation and invasive tests, helping physicians deliver sufficient oxygen with minimum toxicity. Potential sites for oxygen measurement vary between the blood and the mitochondria; each method measures at a different site and detects different types of hypoxia and hyperoxia. Thus, values obtained by two different methods are not equivalent, giving each method unique strengths and weaknesses. We review two clinical methods (pulse oximetry and transcutaneous oximetry), as well as four experimental methods (near-infrared spectrophotometry, magnetic resonance spectroscopy, magnetic resonance saturation imaging, and time-of-flight absorbance spectrophotometry). The principles of each method and the clinical situations in which each succeeds or fails are discussed. A fundamental understanding of each method can help in deciding which methods, if any, are appropriate for a given patient and how best to correct observed oxygenation problems once they are discovered.

Blood Gas Monitoring, Transcutaneous↗

PubMed1991

A spectroscopic analysis of the Pro35----Ala mutant of Rhodobacter capsulatus cytochrome c2. The strictly conserved Pro35 is not structurally essential.

Visible, near-ultraviolet circular dichroic, near-infrared and nuclear magnetic resonance spectroscopies show that the secondary and tertiary structures of the mutant Pro35----Ala Rhodobacter capsulatus ferrocytochrome c2 are similar to the wild-type protein. The near-infrared spectrum shows that the methionine-S--Fe-heme bond is intact; however, a small red shift in the heme M transition of the near-ultraviolet circular dichroic spectrum of the mutant indicates that the heme environment may differ slightly between the two proteins. This difference may be a consequence of changes in the ligand and hydrogen bonds of His17 [Gooley, P. R. & MacKenzie, N. E. (1990) FEBS Lett. 260, 225-228]. 1H and 15N chemical shift differences suggest that the microenvironment of pyrrole rings III and IV of the heme prosthetic group differs between the two proteins. As the rings of the Phe51 and Tyr53 flip faster in the mutant protein than the wild type, these chemical shift differences may reflect changes in the time-average ring-current effects and not structural alterations.

Circular Dichroism↗

PubMed1992

Near-infrared FT-Raman spectra of the rat brain tissues.

Near-infrared Fourier transform (FT) Raman spectroscopy was applied to brain tissues in situ. The spectra were obtained from the cerebral cortex, white matter of the cerebrum, caudate-putamen, thalamus, synaptosomal fraction, and myelin fraction. High-quality Raman spectra in the 400 to 2940 cm-1 range were measured without interference of autofluorescence. Common spectral bands were assigned. The ratios of the intensity at 1664 (amide I), 1442 (CH2 deformation), 2885 (CH2 asymmetric stretching), 2938 cm-1 (CH3 symmetric stretching) could be used for differentiation between the gray and white matters.

Animals↗

PubMed1991

Near-infrared Fourier transform Raman and conventional Raman studies of calf gamma-crystallins in the lyophilized state and in solution.

We present in this report a detailed structural study of calf gamma-crystallins both in the solid state and in solution by the newly developed technique of near-infrared (IR) Fourier transform (FT)-Raman spectroscopy as well as by the conventional Raman method. In comparison with conventional laser Raman spectroscopy, the near-IR FT-Raman approach exhibits several attractive features such as fluorescence rejection capability, frequency accuracy, and the FT's multiplex and throughput advantages. These distinct characteristics combined form the basis for the particular suitability of FT-Raman in crystallin structural analysis and elucidation. We have thus obtained evidence in support of the view that native calf gamma-II crystallin does not contain a disulfide bond either in the lyophilized state or in solution. In addition, conventional Raman spectra are examined for all four gamma-crystallin fractions. gamma-S, gamma-II, gamma-III, and gamma-IV, and the results indicate a high degree of structural similarities among them. It is also found that the sulfhydryl groups in all four gamma-crystallins are highly resistant to air oxidation and are capable of maintaining their reduced state during isolation in the absence of added reductants or such chelating agents as EDTA.

Animals↗

PubMed1991

Quantitation of time- and frequency-resolved optical spectra for the determination of tissue oxygenation.

The recent development of near-infrared time- and frequency-resolved tissue spectroscopy techniques to probe tissue oxygenation and tissue oxygenation kinetics has led to the need for further quantitation of spectroscopic signals. In this paper, we briefly review the theory of light transport in strongly scattering media as monitored in the time and frequency domains, and use this theory to develop algorithms for quantitation of hemoglobin saturation from the photon decay rate (delta log R/delta t) obtained using time-resolved spectroscopy, and from the phase-shift (theta) obtained from frequency-resolved, phase-modulated spectroscopy. To test the relationship of these optical parameters, we studied the behavior of delta log R/delta t and theta as a function of oxygenation in model systems which mimicked the optical properties of tissue. Our results show that deoxygenation at varying hemoglobin concentrations can be monitored with the change in the photon decay kinetics, delta delta log R/delta t in the time-resolved measurements, and with the change in phase-shift, delta theta, in the frequency-resolved technique. Optical spectra of the adult human brain obtained with these two techniques show similar characteristics identified from the model systems.

Algorithms↗

PubMed1992

Identification of urinary calculi by Raman laser fiber optics spectroscopy.

Human calculi of various compositions were automatically identified by using near-infrared excitation Fourier-transform Raman spectrometry. After having built a 150-compound Raman library as a first step, we used a commercial software for infrared spectra (program BIRSY, from Brüker) to determine the composition of different calculi. Good results were obtained for both classical Raman laser and Raman laser fiber optics spectroscopies. With the use of a natural biological medium, e.g., urine, to mimic as closely as possible clinical in vivo conditions, the automatic search correctly identified the calculus composition with relatively good test quality; in some mixtures, however, the results can only be considered semi-quantitative at present, even after smoothing of the spectra.

Fiber Optic Technology↗

PubMed1990

Cytochrome c'' isolated from Methylophilus methylotrophus. An example of bis-histidine-co-ordinated Fe3+ haem, with near-perpendicular orientation of the ligands.

Cytochrome c'' (Methylophilus methylotrophus) is a soluble protein, Mr 15,000, possessing one haem which is high-spin in the reduced state but switches to a low-spin form on oxidation. Low-temperature electron-paramagnetic-resonance spectroscopy of the oxidized state shows a low-spin signal at gz = 3.65 with a folded line-shape typical of a haem of low rhombicity, and the near-infrared magnetic-circular-dichroism (m.c.d.) spectra reveal an unusually intense (delta epsilon = 400 M-1.cm-1 at 5 T, 4.2 K) charge-transfer band at 1560 nm, establishing that the oxidized haem is co-ordinated by two His residues in a near-perpendicular orientation. This conformation is well established for transmembrane b cytochromes, but this appears to be the first example in a water-soluble cytochrome. The low-temperature m.c.d. spectra of the reduced form of the protein confirms that the haem contains a high-spin Fe2+ ligated by one His residue. The redox-linked spin-state change releases a His group. Since this residue is likely to bind a proton at pH values less than 6.5, this cytochrome may provide a useful model of a molecular mechanism of a redox-linked proton uptake and release process.

Bacteria↗

PubMed1991

Fluorescence polarization and low-temperature absorption spectroscopy of a subunit form of light-harvesting complex I from purple photosynthetic bacteria.

Measurements of polarized fluorescence and CD were made on light-harvesting complex 1 and a subunit form of this complex from Rhodospirillum rubrum, Rhodobacter sphaeroides, and Rhodobacter capsulatus. The subunit form of LH1, characterized by a near-infrared absorbance band at approximately 820 nm, was obtained by titration of carotenoid-depleted LH1 complexes with the detergent n-octyl beta-D-glucopyranoside as reported by Miller et al. (1987) [Miller J. F., Hinchigeri, S. B., Parkes-Loach, P. S., Callahan, P. M., Sprinkle, J. R., & Loach, P. A. (1987) Biochemistry 26, 5055-5062]. Fluorescence polarization and CD measurements at 77 K suggest that this subunit form must consist of an interacting bacteriochlorophyll a dimer in all three bacterial species. A small, local decrease in the polarization of the fluorescence is observed upon excitation at the blue side of the absorption band of the B820 subunit. This decrease is ascribed to the presence of a high-energy exciton component, perpendicular to the main low-energy exciton component. From the extent of the depolarization, we estimate the oscillator strength of the high-energy component to be at most 3% of the main absorption band. The optical properties of B820 are best explained by a Bchl a dimer that has a parallel or antiparallel configuration with an angle between the Qy transition dipoles not larger than 33 degrees. The importance of this structure is emphasized by the results showing that core antennas from three different purple bacteria have a similar structure.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteriochlorophylls↗

PubMed1992

Thiobacillus ferrooxidans cytochrome c oxidase: purification, and molecular and enzymatic features.

Cytochrome c oxidase from Thiobacillus ferrooxidans was purified to homogeneity and some of its properties were studied. The oxidase was solubilized with n-octyl-beta-D-thioglucoside (OTG) under acidic conditions (pH 4.0) and purified by one step of ion-exchange chromatography with a CM-Toyopearl column. The absorption spectrum of the oxidase showed peaks at 420 and 595 nm in the oxidized form and at 440 and 595 nm in the reduced form. Its CO compound showed a novel absorption spectrum; a double-peaked gamma band appeared at 429 and 438 nm. The oxidase seemed to have CuA-like copper atom from its ESR and near-infrared spectra. The oxidase molecule consisted of three polypeptides with molecular weights of 53,000, 22,000, and 17,000, respectively, as estimated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The molecular weight of the enzyme in a solution containing detergents was estimated to be 169,000 on the basis of the results obtained by gel filtration, while the molecular weight per heme alpha was estimated to be 83,700. The copper content of the oxidase was 1.01 g atom per mol of heme alpha. Therefore, the cytochrome seemed to contain one molecule of heme alpha and one atom of copper in the minimal structural unit consisting of one molecule each of the three subunits, and to occur as a dimer of the unit in the solution. The oxidase oxidized ferrocytochrome c-552 of the bacterium, and the optimal pH of the reaction was 3.5.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Fractionation↗

PubMed1991

Spectroscopic studies of cobalt and nickel substituted rubredoxin and desulforedoxin.

The single iron site of rubredoxin was replaced by nickel and cobalt. The near-infrared/visible/UV spectra of these metal derivatives show ligand-field transitions and charge-transfer bands which closely resemble those of simple tetrathiolate complexes, indicating a tetrahedral arrangement of the sulfur cysteinyl ligands around the metal core. The 1H NMR spectra of the nickel and cobalt derivatives reveal extremely low-field contact shifted resonances of one proton intensity assigned to beta-CH2 and alpha-CH cysteinyl protons. Other well resolved resonances shifted out of the main protein spectral envelope are also observed and probably arise from contact plus pseudocontact shift mechanisms. Rubredoxins from different sulfate reducers were metal substituted and assignments of aliphatic protons are tentatively proposed, taking advantage of the amino acid sequence homologies. The present data is promising in terms of structural analysis of the coordination sphere of the metal core. It was also shown that replacement of the iron atom of desulforedoxin, a close analogue of rubredoxin, by cobalt and nickel was possible.

Amino Acid Sequence↗