Hormone (3-indoleacetic acid)-phospholipid interaction: 1H, 13C and 31P nuclear magnetic resonance studies

The interaction between the plant hormone, 3-indoleacetic acid (IAA), and some phospholipids in CDCL₃ has been studied by ¹H, ¹³C and ³¹P nuclear magnetic resonance (NMR) spectroscopy. Upon interaction with IAA, significant changes occurred in resonance positions of the phospholipid head group nuclei. Alteration of the fatty acid composition influenced the effects of IAA on these nuclei. These effects were observed in the ethanolamine and phosphate groups of the phosphatidylethanolamines, and in the choline, phosphate and glycerol groups of the phosphatidylcholines. Changes in resonance positions of the phospholipid head group nuclei were used for the determination of dissociation constants (K_d). In all cases, K_d values were approx. 10^?2 molal for 1 : 1 interaction. The NMR results suggest an interaction orientation in which the aromatic ring system of IAA interacts with the quaternary nitrogen function of the head group, and the phosphate group becomes hydrogen-bonded to the NH or carboxyl proton of 1AA.     

Deuterium and carbon-13 tracer studies of ethanol metabolism in the rat by 2H, 1H-decoupled 13C nuclear magnetic resonance

[1-¹³C, 1,1-²H₂] ethanol and [2,2,2-²H₃] ethanol were administered to bile fistula rats. A new technique, ²H, ¹H-decoupled ¹³C nuclear magnetic resonance, was used in attempting to account for the distribution of the isotopic species along the steroid skeleton of 3–45 mg of isolated bile acids. The technique revealed ²H incorporation at many carbon sites unambiguously, but has limitations as a quantitative ²H assay at these levels of sample availability.     

Characterization of the mobility of various chemical groups in the purple membrane of halobacterium halobium by 13C, 31P and 2H solid state N M R

Lyophilized purple membrane sheets have been investigated by C-13- and P-31-cross polarization/magic angle spinning N M R spectroscopy. The high-resolution C-13 spectrum and its non-quaternary suppression version indicate fast protein side-chain motions but a rigid backbone structure on a time scale of roughly < 0.001 to 0.01 s. Three components of exchangeable hydrogen have been detected by deuterium N M R. The mean exchange time of the peptide hydrogens must be longer than 1 μs. The medium component is attributed to mobile side-chains. In addition a narrow line has been observed which is assigned to the residual hydration water.     

Synthesis and properties of 35S, 14C and 3H labeled S-alkyl glycerol ethers and derivatives

Radioactive S-alkyl glycerol ethers have been synthesized with ³⁵S, ¹⁴C and ³H labels as well as ³H/³⁵S double labels.The synthesized compounds were converted to various derivatives which can serve to characterize the S-alkyl glycerol ethers. These included the isopropChemical analysis, IR, NMR, zonal TLC profile scans and GLC showed all the products to be > 99% pure.The GLC behaviour of the aldehyde and acetate derivatives of both S-alkyl glycerol ethers and O-alkyl glycerol ethers on EGSS-X was compared.     

1H-1H and 13C-13C vicinal coupling constants and amino acid side chain conformation in peptides

The vicinal coupling constants ¹³C′-¹³C^γ were measured in aspartic acid and phenylalanine (85 % ¹³C enrichment) as free amino acids and in the peptides Asp-Pro and Gly-Pro-Phe. These coupling constants used in connection with those between the α -and the β-protons provide the unambiguous assignment of rotamers I and II in the Asp and Phe side chains. The method is generally applicable to other amino acids and residues even in large peptides. A possible set of J_g^c,c and J_t^c,c values is proposed for the use of carbon 13-carbon 13 vicinal coupling constants in the side chain conformational studies of amino acid residues with a free carboxyl group.     

A high-resolution NMR study (1H, 13C, 31P) of the interaction of paramagnetic ions with phospholipids in aqueous dispersions

¹H-, ¹³C-and ³¹P-NMR spectra of egg-yolk phosphatidylcholine (PC), phosphatidylserine (PS) and phosphatidic acid (PA) and cosonicated mixtures of these phospholipids were obtained from ultrasonicatcd dispersions containing Pr³⁺, Eu³⁺, Gd³⁺ and Mn²⁺ ions.The differences in chemical shift values. °_n, between the “inner” and “outer” resonance signals for the different nuclei of the polar head group of egg-yolk phosphatidyl choline provide information about the average distances of the paramagnetic ion within the polar groups of the phospholipid molecules. In the Pr(²H₂O)³⁺_n/egg-yolk phosphatidylcholine system the ions are nearest to the phosphate and -CH₂CH₂ group, respectively but relatively far from the N(CH₃)₃ group of the polar head group of the lipid.The integral analysis of the¹ H-NMR spectra obtained from dispersions containing Pr³⁺ and Mn²⁺ ions enables us to calculate the number of the polar groups in both sides of the egg-yolk phosphatidylcholine bilayer, the size of the lipid vesicle and to give some features of the arrangement of the phospholipid molecules in cosonicated egg-yolk phosphatidylcliotine/ phosphatidytserine vesicles. At p²H 8.3 in PC/PS mixtures an extreme asymmetry is observed with PS preferentially in the outer side of the membrane. This side contains approximately three times more PS than PC molecules.Some comments are made concerning the quantitative integral analysis of proton-noise decoupled ³¹ P-NMR spectra as obtained from similar phospholipid mixtures by Michaelson et al. and Berden et at.     

13C-N.M.R.-spectral study of the pH behavior of reductively [13C]methylated,glycophorin a glyco-octapeptides and a related glycopentapeptide

The pH dependence of the labeled-carbon resonances of reductively [¹³C] methylated compounds tri-l-Ser, glyco-octapeptide A^M, asialoglyco-octapeptide A^M, glyco-octapeptide A^N, asialoglyco-octapeptide A^N, and a glycopentapeptide was investigated. The results are discussed relative to those previously observed for reductively [¹³C]methylated, intact glycophorins A^M and A^N, and in terms of the mode of display of the MN blood-group specificities by these related glycoproteins. The results indicated that the α-d-NeuAc groups appear to affect the pH-titration results of glyco-octapeptides A^M and A^N. Moreover, comparison of the pH-titration results for reductively [¹³C]methylated glyco-octapeptide A^M and reductively [¹³C]methylated asialoglyco-octapeptide A^M with those of a reductively [¹³C]methylated glycopentapeptide and reductively [¹³C]methylated tri-l-Ser indicated that the other carbohydrate residues present (α-d-GalNAc and β-d-Gal) may also affect the pH-titration results. The reductive-methylation modification appears to affect the chemical shifts of the carbohydrate and peptide carbon atoms of the glycopentapeptide minimally.     

119Sn Mössbauer spectroscopic studies of the products of the reaction of triorganotin(IV) derivatives with 6-thiopurine

A structural study of the products of the reaction of R₃Sn^IV derivatives (R = Me, Buⁿ, Ph) with 6-thiopurine, 6-TPH₂, and its sodium salt, 6-TPHNa, has been undertaken using Mössbauer spectroscopy and the point-charge model rationalization of the Mössbauer parameter nuclear quadrupole splitting. The synthetic reactions have been carried out at ca. 0 °C, 20 °C and 50 °C. The Mössbauer spectra of the complexes AlK₃Sn(6-TPH) are consistent with the occurrence of two distinct tin(IV) sites in samples prepared at the lower temperature, while one only site appears by increasing the temperature of the reaction. Two tin sites constantly occur in the products of the reactions involving the Ph₃Sn^IV moiety; the stoichiometry is assumed to be (Ph₃Sn)₃(6-TPH)(6-TP) for the uniquely-formed complex. Solid state polymeric structures with trigonal bipyramidal environments of the tin atoms and planar SnC₃ skeletons have been proposed. The apical ligand atoms have been assumed to be N, S and N, N in the samples showing two individual tin(IV) sites, and N, N when a single site was present.     

High resolution nuclear magnetic resonance spectroscopy of glycosphingolipids. I: 360 MHz 1H and 90.5 MHz 13C NMR analysis of galactosylceramides

The high resolution ¹H and ¹³C nuclear magnetic resonance (NMR) spectra of galactosylceramides containing n-fatty acids and α-hydroxy fatty acids were recorded in dimethylsulfoxide solution with and without addition of D₂O. From the coupling constants of the sugar ring protons, a ⁴C₁ conformation can be deduced. In contrast to the conformation in aqueous solution, the C⁶ hydroxymethylene group is freely rotating around the C⁶C⁵ bond. In the ceramide residue all signals produced by protons linked to carbons bearing electronegative substituents could be attributed. The large difference in coupling constants of the methylene protons of C^1′ to the C^2′ methine proton of the sphingosine indicates a restricted rotation around the C^1′C^2′ bond. The assignments of the hydroxy and amino protons follow from the decoupling of the corresponding methine protons.     

1H and 13C nuclear magnetic resonance spectra of the lipids in normal and SV 40 virus-transformed hamster embryo fibroblast membranes

Well resolved ¹H and ¹³C NMR spectra were obtained with normal and SV 40-transformed cell membranes. Estimation of the ratio of ¹³CT₂ values of the normal to transformed cell membranes showed an increased intermolecular motion in the transformed cell membranes. The temperature dependence of the (CH₂)_n line in the ¹H spectra in the temperature range 298–343 °K shows an activation energy for the lateral diffusion of the fluid phospholipid regions in the normal cell membranes while the transformed ones show practically no temperature dependence in this temperature range. The fluidity of the phospholipid region in the transformed cell membrane seems to be significantly higher than that observed in the normal cell material. These data support and extend the findings concerning the mobility of the concanavalin A binding/agglutinating sites on the surface of normal and virus-transformed cells and suggest further approaches to the study of the membrane alterations in tumor cells.     

67Zn and 1H NMR studies of Zn2+-imidazole and carboxylate complexes

⁶⁷Zn NMR studies of naturally abundant Zn²⁺-imidazole and carboxylate ligands Complexes are shown. Thus, quadrupolar relaxation changes in ⁶⁷Zn NMR caused by adding imidazole ligands are more remarkable than those by carboxylate ligands. The changes caused by adding less bulky imidazole ligands are more prominent than those caused by a bulky imidazole ligan. Changes in Zn²⁺ quadrupolar relaxation rate caused by adding a cyclic hexapeptide consisting of L-histidine, L-cystein(Acm) and D-leucine are larger than those by a corresponding linear hexapeptide. Those changes in the quadrupolar relaxation rate of ⁶⁷Zn NMR among Zn²⁺ complexes can be reasonably interpreted in terms of the differences of equilibrium constants of those complexes to a first approximation.     

Dienoic acids,synthesis and 13C NMR spectral analysis

A preparation of E,E-2,4-dienoic acids, together with the assignments of their ¹³C NMR signals and the shifts observed after transformation into their sodium salts, is described. The stereochemistry of the double bonds of 3,5-dienoic esters, obtained from 2,4-dienoic acids, on the basis of ¹³C NMR data, is also presented.     

13C nmr studies of aurothioglucose: Ligand exchange and redox disproportionation reactions

¹³C nmr studies of gold thioglucose, AuSTg, and solutions containing added β-1-D-thioglucose, TgSH, have been conducted at PD 7.4 and interpreted in terms of complexation and ligand exchange reactions that are consistent with the known preference of gold(I) for linear two-coordinate structures. The upper limit of the half-life for ligand exchange between 0.25 M Au(STg)₂^? and TgSH at pD 7.4 is 2.2 msec. The ¹³C nmr spectra of various thioglucose derivatives have been assigned. A novel oxidation reduction reaction was discovered that leads to the formation of metallic gold and a product tentatively identified as the sulfinic acid derivative of thioglucose. The presence of sulfinic acid in AuSTg was indicated by the infrared absorption at 1050 cm^?1. The same product was formed by slow hydrolysis of thioglucose disulfide. A mechanism for the formation of the sulfinic acid derivative from AuSTg is proposed.     

Metal ion-biomolecule interactions. XII. 1H and 13C NMR evidence for the preferred reaction of thymidine over guanosine in exchange and competition reactions with Mercury(II) and Methylmercury(II)

Mercury(II) bridge complexes of the type [Nuc-Hg-Nuc] (Nuc = thymidine or guanosine), and methylmercury(II) complexes of thymidine and guanosine of the type [CH₃Hg(Nuc)], have been prepared under appropriate conditions of pH and reactant's stochiometry in acqueous soluton. The various complexes have been characterized by ¹H and ¹³C NMR and used as probes, in competition and exchange studies, to establish the relative affinities of Hg(II) and CH₃Hg(II) towards the nucleosides guanosine and thymidine. These studies have confirmed that Hg(II) and CH₃Hg(II) bind to N₃ of thymidine in preference to N₁ of guanosine. The studies further show that reactions of mercury(II) with the nucleosides are thermodynamically controlled; the preperential binding reflects the relative stabilities of the respective complexes.