Nuclear Magnetic Resonance Spectrum of Deamino-Lysine-Vasopressin in Aqueous Solution and Its Structural Implications

The peaks in the proton nuclear magnetic resonance spectrum of deamino-lysine-vasopressin in aqueous solution at pH values between 3 and 5 were assigned to particular amino-acid residues by use of the results of transfer-of-saturation studies, NH-C(alpha)H and C(alpha)H-C(beta)H decoupling experiments, and other data. The conformation of deamino-lysine-vasopressin in water differs from that of lysine-vasopressin in the same solvent.     

Nuclear Magnetic Resonance Spectrum of Lysine-Vasopressin in Aqueous Solution and Its Structural Implications

The peaks in the proton NMR spectrum of lysine-vasopressin in aqueous solution at pH 3-5 were assigned to particular amino-acid residues by the use of the results of dilution studies and NH-C^αH and C^αH-C^βH decoupling experiments. The conformation of lysine-vasopressin in water differs from its conformation in dimethylsulfoxide.     

Tertiary Hydrogen Bonds in the Solution Structure of Transfer RNA

The high resolution nuclear magnetic resonance (NMR) spectra of hydrogen-bonded protons in four tRNAs have been studied at 270 MHz. The relative intensity of the resonances between -11 ppm and -15 ppm of Escherichia coli tRNA₁^Val indicate that there are 26 ± 3 protons, while only 20 are expected from secondary structure Watson-Crick hydrogen bonds in the cloverleaf structure. Several possible candidates for these extra resonances are suggested by tertiary interactions observed in recent crystallographic studies.     

Nuclear Magnetic Resonance Spectrum of Lysine-Vasopressin and Its Structural Implications

The NMR spectra at 220 MHz of lysinevasopressin and its precursors were measured in dimethyl sulfoxide, and the peaks were assigned to specific protons. Information about hydrogen bonding was obtained from the temperature coefficients of the chemical shifts. With these data, and with several chemical-shift positions and coupling constants, structural information was derived for this polypeptide hormone.     

Nuclear Magnetic Resonance Studies of Lysine-Vasopressin: Structural Constraints

The 220-MHz proton NMR spectra of lysine-vasopressin and some related compounds are examined in deuterated dimethyl sulfoxide to obtain structural information that must be satisfied by any proposed conformation of the molecule. This structural information is in the form of dihedral angles (for rotation about the NH-C^αH bonds) from coupling constants, possible hydrogen bonding of the CONH₂ and backbone amide groups from the temperature-dependence of the chemical shift, and aromatic ring-aromatic ring interaction from the effect of the magnetically anisotropic groups on the chemical shift.     

Nuclear Magnetic Resonance Determination of the Angle Ψ in Peptides

A simple theoretical model is used to suggest that the NCCH coupling constant, Jnh, has a dihedral angle dependence that can serve for estimating the angle Psi in peptides. Some experimental comparisons are made to test the model; they include a new measurement of Jnh in N-acetylglycine.     

Studies of Transfer RNA Tertiary Structure by Singlet-Singlet Energy Transfer

Five species of tRNAs bearing two different fluorescent groups were synthesized. These were suitable for intramolecular distance measurements by singlet-singlet energy transfer. The efficiency of energy transfer was determined from the sensitized emission of the energy acceptor. With the assumption that the relative orientation of donor and acceptor is random, the apparent distances between the 5'-end and the 3'-end, the 4-thiouridine and the 3'-end, the pseudouridine and 3'-end, the pseudouridine and the dihydrouridine in Escherichia coli formyl methionine tRNA, and between the 2-thiouridine (in the anticodon) and the 3'-end in E. coli glutamate tRNA were calculated to be 24 A, 38 A, 55 A, 36 A, and >65 A, respectively.     

Studies of Transfer RNA Tertiary Structure by Singlet-Singlet Energy Transfer

This distance between a base next to the anticodon of tRNA and the 3' CpCpA terminus of the molecule has been estimated by singlet-singlet energy transfer experiments. The energy donor was the Y base of unknown structure found in yeast tRNA(phe). Three different energy acceptors were used: acriflavine, proflavinyl acetic acid hydrazide, and 9-hydrazino acridine. These were attached to the periodate-oxidized 3' end of the tRNA. R(0)'s between 24 and 30 A were calculated for the three chromophore couples by assuming that the relative orientation of donor and acceptor is random. This assumption is supported by the consistency of the experimental results with all three acceptors and by studies of the fluorescence depolarization of Y. The energy transfer observed both by quenching of Y and enhanced activation of the acceptors is quite small, indicating that the anticodon is more than 40 A away from the amino acid accepting terminus. This places severe restrictions on the type of tertiary structure possible for tRNA.     

Human Tumors Detected by Nuclear Magnetic Resonance

Measurements of the water proton spinlattice relaxation (T(1)) in 106 human tumors confirms earlier results with animals [Damadian, R. (1971) Science 171, 1151-1153]. T(1) of all the tumors studied were significantly longer than T(1) of the corresponding normal tissues. Mean standard error and range were reported for T(1) of every human organ and for all the tumor groups studied. The technique is now ready for use by pathologists as an adjunct to present methods of diagnosing malignancy.     

Computed Tomography and Magnetic Resonance Imaging Features of Primary and Secondary Hepatic Glycogenosis

Glycogen storage disease type I and glycogenic hepatopathy are the most common type of primary and secondary hepatic glycogenosis, with presenting common radiological features of hepatomegaly, hepatic signal, or density change. Beyond that, glycogen storage disease type I shows hepatocellular adenomas or fatty liver, while glycogenic hepatopathy does not.     

Phosphate Metabolism in Intact Human Erythrocytes: Determination by Phosphorus-31 Nuclear Magnetic Resonance Spectroscopy

Whole human blood was examined by (31)P nuclear magnetic resonance spectroscopy. Individual phosphates (alpha,beta,gamma) of ATP were identifiable, and two microenvironments appeared to be present for this molecule. When sequential recordings of freshly collected blood were made, 2,3-diphosphoglycerate was observed to decrease in association with a concomitant increase in inorganic orthophosphate. When aged cells containing little 2,3-diphosphoglycerate were incubated in the presence of inosine and pyruvate, 2,3-diphosphoglycerate formation could be demonstrated. These results show that cellular metabolism can be recorded directly in intact cells by (31)P nuclear magnetic resonance.     

Lanthanide Ion-Induced Isotropic Shifts and Broadening for Nuclear Magnetic Resonance Structural Analysis of Model Membranes

The effects of a series of aquated lanthanide ions on the nuclear magnetic resonance spectrum of phospholipid bilayer suspensions are reported. The ability of these ions to provide a spectral distinction between morphologically exterior resonances and their interior counterparts was confirmed. Measurements of the relative shifting and broadening capabilities of these ions are reported, and their correlation with solid-state magnetic susceptibility anisotropies is shown to implicate a dipolar (pseudocontact) mechanism as the source of this effect. The potential for the use of dipolar shifts as structural probes is discussed and an alternative method using dipolar shifting and broadening reagents simultaneously is presented.     

Carbon-13 Nuclear Magnetic Resonance Spectroscopy. Structure of the Anticoagulant Warfarin and Related Compounds in Solution

Carbon-13 nuclear magnetic resonance spectra have been obtained for the coumarin-related compounds warfarin and phenprocoumon. The spectral assignments indicate that warfarin exists as a mixture of cyclic hemiketal diastereomers in dimethyl sulfoxide solution. The sodium salt of warfarin exists as the ringopen form in water solution.     

Transfer RNA Conformation in Solution Investigated by Isotope Labeling

The incorporation of tritium into the C-8 position of purine residues in yeast tRNA^Phe is shown to be markedly dependent on the conformation of the molecule. The completely unfolded molecule incorporates tritium at a rate commensurate to that expected for free purine nucleotides, but partially or completely folded forms incorporate proportionately less. The labeling of specific purine sites is determined by digesting the nucleic acid with a specific nuclease and analyzing each of the radioactive fragments produced. This analysis reveals that the amount of labeling of a purine in the folded form is strongly dependent upon its position in the sequence, whereas purine labeling in the unfolded form is independent of sequence position. The labeling pattern of the different bases in the folded form agrees fairly well with what is expected, based on existing solution and x-ray data on the conformation, i.e., residues involved in helical sections or apparently masked by tertiary interactions label more slowly than those on the “outside” of the molecule. Finally, folding and unfolding of specific regions of the macromolecule may be followed by the isotope labeling.     

Carbon-13 Magnetic Resonance Evaluation of Polypeptide Secondary Structure and Correlation with Proton Magnetic Resonance Studies

With the use of appropriately chosen solvent pairs it is demonstrated that solvent dependence of peptide carbonyl carbon resonances can be correlated with polypeptide secondary structure. Solvent titrations show the peptide carbonyl which is intramolecularly hydrogen bonded to exhibit less chemical shift on going from a dimethylsulfoxide solution to a solution containing a solvent which is a good proton (or deuteron) donor. Effective solvent systems are dimethylsulfoxide paired with water, trifluoroethanol, or methanol. This approach is demonstrated with the pentapeptide of elastin.     

Proton-Enhanced 13C Nuclear Magnetic Resonance of Lipids and Biomembranes

A recently developed nuclear double resonance technique which permits sensitive detection, together with high resolution, of rare spins in solids or other dipolar-coupled nuclear systems [Pines, Gibby, and Waugh (1973) J. Chem. Phys. 59, 569] has been applied to the study of natural abundance (13)C-nuclear magnetic resonance in lipid mesophases and of selectively labeled carbon sites in bacterial membranes.Detailed microscopic information on the molecular organization and phase transitions of the lipid phases and their interaction with ions and other molecules can be obtained from the study of the chemical shift anisotropies and dynamical aspects of the (13)C NMR spectra of unsonicated lipid dispersions (liposomes). Experiments are reported which demonstrated the feasibility of quantitatively observing the (13)C-nuclear magnetic resonance of specifically labeled sites in unperturbed Escherichia coli membrane vesicles for the study of the physical state of the lipids with the aim of relating it to the known lipid-dependent functional properties of the membranes.     

Conformational Studies on Tocinamide and Deaminotocinamide by 220 MHz Nuclear Magnetic Resonance Spectroscopy

The 220 MHz spectra of tocinamide and deaminotocinamide, the ring moieties of oxytocin and of deamino-oxytocin, respectively, were investigated in [U-(2)H]dimethylsulfoxide solution. Extensive decoupling and exchange experiments allow complete spectral assignment and determination of many coupling constants. Circular dichroism spectra assigned a right-hand screw sense to the C-S-S-C group. The conformations of tocinamide and deaminotocinamide are different from each other and from those suggested for the ring portions of oxytocin and deamino-oxytocin. The relationship of this difference to biological activity is commented upon. The importance of the interaction of the side chain with the ring in oxytocin and deamino-oxytocin is emphasized.     

31P Nuclear Magnetic Resonance Spectroscopy of Native and Recombined Lipoproteins

Native and recombined lipoproteins have been studied by (31)P nuclear magnetic resonance spectroscopy. Very low-, low-, and high-density lipoproteins exhibited characteristic spectra. The main resonances were assigned to phosphatidylcholine and sphingomyelin. Relaxation times for these phospholipids were separately measured in low-density lipoproteins and high-density lipoproteins. The effect of paramagnetic ions (Eu(+++)) on the nuclear magnetic resonance spectrum of high-density lipoproteins is reported.     

Proton Nuclear Magnetic Resonance Studies of Myoglobin in H2O

Exchangeable hydrogens in proteins can be identified by comparison of nuclear magnetic resonance spectra obtained in H(2)O and in D(2)O. In oxymyoglobin and myoglobin we have been able to observe resonances of the NH protons of the two tryptophans, as well as one resonance from arginine and one from histidine in the range -10 to -15 ppm downfield from 3-(trimethylsilyl)propanesulfonic acid (sodium salt). These resonances have been identified by chemical modifications coupled with considerations of crystallographic structure and the dependence of the resonances on the species (sperm whale, porpoise, horse) from which the myglobin was obtained and on spin, pH, and temperature.