[en] To facilitate in vivo NMR studies of microorganisms under stable environmental conditions a technique was developed in which algae are embedded in Ca-alginate beads and continuously perfused during the measurements. Dunaliella salina was shown to grow, multiply and recover frm osmotic shocks while embedded within the beads. Using this technique the detailed kinetics of glycerol metabolism of Dunaliella salina following an osmotic shock, were investigated

[en] The solution conformation of a 33-residue peptide segment, derived from the TonB protein which is implicated in bacterial membrane transport processes, has been investigated using high-resolution proton magnetic resonance techniques. This proline-rich peptide possesses sequence-imposed sections of elongated secondary structure that must be retained in the native protein configuration. These structural constraints provide elements of stiffness that imply a purely structural role for TonB and are relevant to the subcellular location and biological role of the protein. On the basis of these data we suggest that this protein spans the periplasmic space, linking the inner and outer membrane components of TonB-dependent transport systems. (Auth.)

[en] Pyruvate decarboxylase (PDC) contains thiamine pyrophosphate (TPP) and Mg²⁺ as cofactors. ³¹P NMR studies with PDC in the presence of added Mn²⁺ reveal the pyrophosphate moiety of TPP to be a nonaccessible area for the external Mn²⁺ and thus proving the Mg-P-complex (taking part in the binding of the coenzyme to the protein) to be a nonaccessible area for the medium. Glyoxylic acid, acting as an inhibitor of PDC by forming a noncleavable bond with the catalytic center of TPP causes a steric immobilization of the coenzyme indicated by a line broadening of the pyrophosphate moiety. 12 refs.; 3 figs

[en] ¹³C-NMR spectra of whole native cells of Methylobacterium AM1 show dominant signals belonging to poly(β-hydroxybutyrate) and trehalose. Fractionation of the cells demonstrates that the poly(β-hydroxybutyrate) is located in the storage granules and that the trehalose is located in the cytosol. The observation of relatively sharp poly(β-hydroxybutyrate) signals indicates that the polymer granule in this organism is in a mobile rather than truly solid state in vivo. 17 refs.; 1 figure; 1 table

[en] The ¹H-NMR spectra of a series of pyridylamino (PA-) derivatives of oligosaccharides were obtained and compared with those of the corresponding asparagine-linked sugar chains in order to elucidate the effect of the PA-group on the chemical shifts of structural-reporter signals. The effects were found to be localized within the two residues from the end group. Thus, the data for asparagine-linked chains in the literature are applicable to PA-derivatives, so the combination of pyridylamination and NMR measurements greatly reduces the time required for structure analysis of sugar chains of glycoproteins, because the isolation and purification of the chains as PA-derivatives are easy and efficient. (Auth.)

[en] The determination of protein structure by NMR is restricted at molecular masses above 10 k Da by overlapping resonances. One way of overcoming this problem is to label the protein with ¹⁵N. The conventional way to record ¹⁵N spectra is to use heteronuclear multiple-quantum coherence. We present here an alternative approach based on ¹⁵N single-quantum coherence. This is shown to have substantial advantages over the multiple-quantum method, including better F₁ resolution. (author). 23 refs.; 2 figs

[en] The binding of folate to Lactobacillus casei dihydrofolate reductase in the presence and absence of NADP⁺ has been studied by ¹⁵N NMR, using [5-¹⁵N]folate. In the presence of NADP⁺, three separate signals were observed for the single ¹⁵N atom, in agreement with our earlier evidence from ¹H and ¹³C NMR for multiple conformations of this complex. The ¹⁵N spectra of the binary enzyme-folate complex provide evidence for the first time that this complex also exists in at least two conformational states. This is confirmed by the observation of two separate resonances for the 7-proton of bound folate, located by two-dimensional exchange spectroscopy. 15 refs.; 3 figs.; 1 table

[en] The authors present the results of a new NMR-based procedure for measuring the fast transmembrane exchange of D-[1-¹³C]glucose in human erythrocytes. The method relies on different rates of exchange between the α- and β-anomers of glucose inside and outside the cells; the rate outside the cells is greatly increased by the addition of mutarotase to the suspension. Theory is developed to describe nuclear-spin transfer in the present system and is used to analyse the data to yield estimates of transmembrane-exchange rate constants and their statistical uncertainties. For a total glucose concentration of 25.5 mmol/l at 40⁰C the first order efflux rate constants for the α- and β-anomers were 1.20 ± 0.40 s^-1 and 0.71 ± 0.30 s^-1, respectively. 17 refs.; 4 figs

[en] Met⁵-enkephalin - a pentapeptide (Tyr-Gly-Gly-Phe-Met) - can exist in two possible folded arrangements with a rigid two-hydrogen-bonded network. In one arrangement, a Gly 2-Gly 3 β-bend is formed and in the other a Gly 3-Phe 4 β-bend. The two conformations are distinguished by the spatial relation of Tyr 1 and Phe 4: in the Gly 2-Gly 3 β-bend, Tyr 1 and Phe 4 can be brought close to each other while in the Gly 3-Phe 4 β-bend they are far apart the authors have utilized one-dimensional nuclear Overhauser effect (NOE) measurements between the ring protons of Tyr 1 and Phe 4 to determine their proximity. The NOE data clearly show that a pair of protons, one each from Tyr 1 and Phe 4, are as close as 3.3 A while other inter-proton distances are beyond 4.5 A. Therefore, the authors propose the presence of a Gly 2-Gly 3 β-bend for Met⁵-enkephalin in solution. The structure of Met⁵-enkephalin in solution is very similar to the single crystal structure of Leu⁵-enkephalin and tends to explain the biological activity data of several modified enkephalins. (Auth.)

[en] A full understanding of the central role of P_i in photosynthesis requires information on the size of the endogenous P_i pools and the extent to which they interact with each other under different physiological conditions. In vivo ³¹P-NMR spectroscopy has the potential to assist in this objective by the early applications of this technique to leaf tissues were disappointing. Here we report ³¹P-NMR data from maize and tomato leaf discs that: (i) cast doubt on earlier estimates of the cytoplasmic orthophophate pool size; and (ii) prove that exogenously supplied D-mannose can reduce the cytoplasmic P₁level in some circumstances. (author). 21 refs.; 4 figs.; 1 tab