Walter V. Gerasimowicz

Vibrational analysis of amino acids: cysteine, serine, β-chloroalanine

Abstract Normal coordinate calculations were carried out involving a total of seven isotopically substituted analogs of the amino acids cysteine, serine, and β-chloroalanine. Raman spectra were obtained for polycrystalline β-chloroalanine and the ND3 analog. Overlay calculations were employed to obtain 55 force constants which reproduce 206 observed frequencies of seven molecules with an average error of ca. 9 cm−1. The valence force field used was based on local symmetry coordinates. Band assignments were based on the potential energy distribution. About 60% of the normal modes of the seven isotopomers can be called group vibrations by the PED criterion. Most skeletal stretching and bending vibrations are highly mixed and cannot be assigned to individual bond stretching or angle deformation modes.

Resolution-enhanced FT-IR spectra of soil constituents: humic acid

Fourier deconvolution and second-derivative spectroscopy have been used to enhance the resolution of infrared spectra of humic acid (HA) extracted from dried municipal waste. The results demonstrate the extent to which the use of such resolution enhancement techniques can disclose new valuable information concerning the composition of complex heterogeneous samples. The findings are in good agreement with previously obtained solid-state NMR results.

Ripening-related perturbations in apple cell wall nuclear spin dynamics

Abstract Spin-lattice ( 1 H T 1 , 23 Na + T 1 ) and rotating frame spin-lattice ( 1 H T 1 p , 13 C T 1 p ) relaxation times were measured on intact, critical point dried apple tissue at various degrees of ripeness using cross polarization and magic angle spinning (CPMAS) NMR techniques. Solid state carbonyl (δ172) 13 C T 1 p and 23 Na + -carboxylate anion T 1 values, which are inversely proportional to carboxylate reorientation rates, decreased 15–19% during the time course study. Carbonyl resonance 1 H T 1 s diminished by 63% as the tissue softened; a maximal decline of 42% was also observed in the 1 H T 1 s of nonspecific carbohydrate ring carbon signals (δ74) indicating an increase in both acidic and neutral polymer motion. Treatment of the cell wall with polygalacturonase resulted in a significant decrease in both carbonyl and ring carbon 1 H T 1 s (57 and 42%, respectively) demonstrating the important structural function of polyuronides not only in the middle lamellae but also in the primary cell wall.

Effects of aluminum on the release and-or immobilization of soluble phosphate in corn root tissue: a 31P-nuclear magnetic resonance study

The effects of aluminum ions on the generation of mobile inorganic phosphate (Pi) within the cells of excised maize (Zea mays L.) root tips were examined using 31P-nuclear magnetic resonance (31P-NMR) spectroscopy. When perfused with a solution containing 50 mM glucose and 0.1–5.0 mM Ca2+ at pH 4.0, 3–5-mm-long excised maize root tips from 3-d-old seedlings showed a significant (approx. 100%) increase in the amount of mobile Pi, (primarily vacuolar) over a period of 30 h. This increase was above that which can be accounted for by the hydrolysis of endogenous sugar phosphates and nucleotides. A change of the pH of the perfusion solution to 7.0 reduced the increase in Pi to approx. 50%. Omission of Ca2+ in the solution at pH 4.0 caused the mobile Pi to increase to about 170%. However, the presence of Al3+ or both Ca2+ and Al3+ in the solution resulted in a significant loss (35–50%) of mostly vacuolar Pi over the same period of time. When root tips containing up to 65% of newly released Pi, produced after 20 h perfusion, were exposed to Al3+, no additional increase in the level of the mobile-Pi signal area was noted. Exposure to Al3+ with Ca2+ and glucose under hypoxia at pH 4.0 resulted in a threefold decrease in intracellular Pi content after the root tips were returned to aerobic conditions. These results indicate that external pH plays an important role in the generation of mobile intracellular Pi and that the presence of both Ca2+ and Al3+ can independently suppress the production of this excess Pi and ultimately reduce the vacuolar Pi.

Interaction of water with clay minerals as studied by 2H nuclear magnetic resonance spectroscopy

Abstract The interaction of water with a series of Ca2+/Na+ , Ca2+/NH4+, and NH4+/Na+-exchanged hectorite and saponite clays in water- and clay-dominated systems was studied using 2H NMR. Variabletemperature Nuclear Magnetic Resonance (NMR) (in the range of 189–299 K) was also used to determine the frequency of exchange and the rotation activation energy between water molecules hydrating the cations and the free water of the tactoid. The 2H quadrupolar splitting and spin-lattice relaxation time (T1) are related to the ratio of clay to adsorbed water in these systems. In water-dominated systems (where clay/water ratio ≪ 1), motional averaging occurs between water hydrating the cations and the “free” or bulk water of the tactoid. In these systems, the spin-lattice relaxation time (T1) is dominated by the relaxation of the “free” water on the external surface of the tactoids and has a value close to that for D2O (0.436 s), with the rotational correlation time (τc) approaching 2.93 × 10−12 s. A more recent article places τc at 1.95 × 10−12 s. The clay systems in this study have clay/ water ratios (=0.0238 g-clay/mL-D2O), and the quadrupolar splittings are of the order of 100 Hz or less. Splittings of In clay-dominated systems with extremely low water contents (clay/water ratio > 1 g-clay/mL-D2O), less motional averaging occurs. Rotational correlation times are slower and greater residual quadrupolar splittings are also observed. Increased residual quadrupolar splittings are observed with increasing clay/ water ratios. For a Na-exchanged hectorite sample (5.31 g-clay/mL-D2O), the quadrupolar splittings are of the order of 12 kHz, and for a Na-exchanged saponite (4.05 g-clay/mL-D2O), the quadrupolar splittings are of the order of 11 kHz. Rotational activation energies (Ea) of 37.8 kJ-mole−1 (9.0 kcal · mole−1) for adsorbed water molecules on Na-exchanged hectorite and 27.2 kJ · mole−1 (6.5 kcal · mole”−1) for Na-exchanged saponite were calculated from spin-lattice relaxation (T1) measurements. These values compare with calculated activation energies of rotation (8.5 kcal · mole−1) for water of hydration adsorbed to a Na-exchanged vermiculite.

FT-IR Spectra of Soil Constituents: Fulvic Acid and Fulvic Acid Complex with Ferric Ions

FT-IR spectra and corresponding second-derivative spectra, as well as pertinent difference spectra, of fulvic acid and of fulvic acid complexed with ferric ions have been obtained. The data reveal that the major functional groups present in the fulvic acid studied are carboxyl groupings and CH2 groupings of hydrocarbon chains. The presence of ferric ions results in increased ionization of the COOH groups to form COO− ions, as well as a change of the characteristic COO− stretching frequencies of the carboxylate ions. The data thus indicate that ferric ions in soils interact with carboxylate ions of fulvic acids. The second-derivative spectra permit the identification of certain alkyl and aromatic hydrocarbon vibrational modes which cannot be observed in the original FT-IR spectra.

Normal coordinate analysis of methanethiol and isotopic analogs

Abstract Gas-phase infrared frequencies for 55 fundamentals of methanethiol (CH2SH) and its d1, d3, d4, and 13C-substituted analogs have been used to calculate a nineteen-parameter symmetry valence force field. The final refinement resulted in an average error of less than 5 cm−1 (ca. 0.4%) between the calculated and observed frequencies for the five isotopomers. In general, the calculations support presently accepted vibrational assignments for these species. One revision indicated, however, is the transposition of δCSH and νCS for CD3SH. The calculations show that the band observed at 643 cm−1 is associated with δCSH, while νCS is assigned to the absorption at 688 cm−1. Comparisons are made between the present force field and one previously reported for CH3SH, as well as one for the selenium analog, CH3SeH. The calculated symmetry valence force field was then transformed ito a set of valence force constants in terms of internal coordinates for comparison with available data for CH3OH, a series of alkanethiols and alkyl sulfides, and an ab initio force field for CH3SH.

Role of the Vacuole in Metal Ion Trapping as Studied by in Vivo 31P-NMR Spectroscopy

31P-NMR spectroscopy has been extensively used to study the energetic profiles in intact plant tissues (Roberts and Jardetzsky, 1981; Roberts, 1984; Loughman and Ratcliffe, 1984). These reports clearly demonstrate that this technique can be used to measure energy status, ATP/ADP ratio (Roberts et al., 1985), changes in intracellular pH (Roberts et al., 1981), effects of hypoxia (Roberts et al., 1984), phosphate movement (Rebeille et al., 1983), and aluminium ion toxicity (Pfeffer et al., 1986).

Vibrational Spectra, Assignments, and Valence Force Field for S-nitrosocysteine and Isotopic Analogs

S-nitrosocysteine and the isotopically-substituted S15NO and N-d3 analogs have been prepared. FT-IR spectra have been obtained on the normal molecule and the 15N isotopomer. Spectra of the N-d3 analog were obtained with a dispersive instrument. The fundamental frequencies of the three isotopomers were calculated by using force constants previously obtained through overlay calculations on amino acids and from a normal coordinate analysis of methyl thionitrite. The average computational error between the observed and calculated frequencies using the transferred force constants was 11 cm−1. This difference was decreased to 7 cm−1 by slightly modifying some of the force constant values by a least-squares refinement. Vibrational assignments are made for all three isotopic analogs by utilizing the potential energy distribution. Out of a total of 96 fundamentals occurring above 300 cm−1, 65 may be classified as group vibrations by the potential energy criterion.

13C NMR Determination of Isomer Formation in Deamination of Poly-L-Lysine

The classical mechanism for the nitrous acid deamination of primary aliphatic amines at low pH calls for formation of carbocation ion intermediates, which react further to yield primary and secondary alcohols and alkenes. More concerted mechanisms may also provide the same product distribution. To examine the reactions between proteins and environmental nitrite, we recently investigated the deamination of e-amino groups of poly-L-lysine at low pH as a model system using 13C NMR to determine the structures of the two new amino acids generated by the deamination reaction. Although reactions of other amino acid side chains with nitrite have been studied, deamination of e-amino groups has received little attention.