Proton magnetic resonance studies of bradykinin antagonists

Bradykinin (BK) is a peptide hormone with sequence Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9 and has been implicated in a multitude of pathophysiological processes such as the ability to lower systemic blood pressure and stimulate pain. BK analogues having bulky, beta-branched D-aliphatic residues at position 7 combined with bulky L-aliphatic residues at position 8 have now been observed to be strong antagonists. Conformational studies based on two-dimensional nmr experiments in methanol/water (80/20 v/v) were carried out on several such active antagonists in a polar solvent. Included in this study were the very active antagonists, [D-Arg0,Hyp3,Thi5,D-Cpg7,Cpg8]-BK [Cpg: alpha-cyclo-pentyl-glycine; Hyp: trans-4-hydroxy-L-proline; Thi: beta-(2-thienyl)-L-alanine] (I), [D-Arg0,Hyp3,D-Cpg7,Cpg8]-BK (II), as well as its variant with D-Cpg7 replaced by Cpg7, namely [D-Arg0,Hyp3,Cpg7,Cpg8]-BK (III). A turn-like structure, which coexists with the extended conformation, was observed between residues 2 and 5 for the most active antagonists I and II, in direct correlation with the peptide activities. No turn-like structure was found for residues 6-9. In peptide III, a turn-like structure was not identified. The existence of a turn at the C-terminal end of bradykinin and its analogues has been predicted by empirical calculations and supported by nmr measurements. But the present nmr study on the most active antagonists (I, II) does not support this hypothesis. Instead, the data suggest that a turn-like structure between residues 2 and 5 could be important for antagonist activity. Finally, one weak inhibitor [D-Cpg7]-BK (IV) showed no defined secondary structure.     

Proton nuclear magnetic resonance spectral profiles of urine in type II diabetic patients

Serial urine samples of 33 type II diabetic patients and 20 control subjects were examined by 1H nuclear magnetic resonance (NMR). Metabolites including lactate, citrate, glycine, alanine, hippurate, trimethylamine-N-oxide, and dimethylamine were identified in all subjects although in higher concentrations in diabetic patients. Other analytes, such as creatine, acetate, betaine, and ketone bodies, were found more frequently and in greater concentrations in diabetics than in controls. In addition, although lactate, citrate, alanine, and hippurate concentrations increased with increasing glycosuria and glycohemoglobin, trimethylamine-N-oxide and dimethylamine were present at high concentrations even in diabetics with good metabolic control. 1H NMR spectroscopy permitted us to explore the relationships among the metabolites present in the urine samples and to obtain information about the disease status in type II diabetic patients.     

Proton nuclear magnetic resonance studies on huwentoxin-I from the venom of the spider Selenocosmia huwena: 1. Sequence-specific 1H-NMR assignments

The complete sequence-specific assignments of resonances in the 1H-NMR spectrum of huwentoxin-I from the Chinese bird spider, Selencocosmia huwena, is described. A combination of two-dimensional NMR experiments including 2D-COSY, 2D-NOESY, and 2D-TOCSY has been employed on samples of the toxin dissolved in D2O and in H2O for assignment purposes. Protons belonging to spin systems for each of the 33 amino acids were identified. The sequence-specific assignments were facilitated by the identification of d alpha N connectivities on the fingerprint regions of the COSY and NOESY spectra and were supported by the identification of dNN and d alpha N connectivities in the TOCSY and NOESY spectra. These studies provide a basis for the determination of the solution-phase conformation of this toxin.     

Proton magnetic resonance spectroscopy in primary blepharospasm

Single-volume proton magnetic resonance spectroscopy, localized to basal ganglia, was carried out in 10 patients with primary blepharospasm (PB) to assess the levels of N-acetyl aspartate (NAA), creatine-phosphocreatine, and choline-containing compounds. NAA was reduced significantly in patients compared with control subjects. This result suggests a striatal neuronal loss in PB.     

Proton nuclear magnetic resonance and distance geometry/simulated annealing studies on the variant-1 neurotoxin from the New World scorpion Centruroides sculpturatus Ewing

The sequence-specific proton resonance assignments for the variant-1 (CsE-v1) neurotoxin from the venom of the New World scorpion Centruroides sculpturatus Ewing (range Southwestern United States) have been performed by 2D 1H NMR spectroscopy at 600 MHz. The stereospecific assignments for the beta-methylene protons of 19 non-proline residues have been determined. A number of short-, medium-, and long-range NOESY contacts as well as the backbone and the side-chain vicinal coupling constants for several residues have been determined. Slowly exchanging amide hydrogens from a number of residues have been identified. On the basis of the NMR data, the solution structure of this protein has been determined by a hybrid procedure consisting of distance geometry and dynamical simulated annealing refinement calculations. Distance constraints from the NOESY data and torsion angle constraints from proton vicinal coupling constant data were used in the simulated annealing calculations. The three-dimensional structure of CsE-v1 is characterized by a three-stranded antiparallel beta-sheet, a short alpha-helix, a cis-proline, and intervening loops. A comparison with the solution NMR data of a homologous protein (CsE-v3) from the Centruroides venom, shows that the structures are essentially similar, except for some minor differences. Some of the NMR spectral perturbations are felt in regions far removed from sites of amino acid substitutions. The hydrophobic surface in CsE-v1 is slightly more extended than in CsE-v3.     

Structure of a mycobacterial polysaccharide-fatty acyl-CoA complex: nuclear magnetic resonance studies

MMP, a linear alpha 1 leads to 4 linked polymer of 3-O-methylmannose, regulates the fatty acid synthetase from Mycobacterium smegmatis by forming stoichiometric complexes with the long-chain acyl-CoA synthetase products. In agreement with previous proposals [Bloch, K. (1977) in Advances in Enzymology and Related Areas of Molecular Biology, ed. Meister, A. (Wiley, New York), Vol. 45, pp. 1-84], nuclear magnetic resonance studies show that the polysaccharide, a random coil in its free form, undergoes a major conformational transition upon enclosing long-chain acyl-CoA. The polysaccharide, probably in helical conformation in the complexed form, interacts with both the paraffinic chain and the CoA moieties of the included fatty acyl thioester.     

Proton magnetic resonance spectroscopy of excised pig liver

After evaluating ex vivo pig liver by 1H magnetic resonance spectroscopy (1H-MRS) using a 1.5 Tesla super-conducting unit, the assignment of peaks was reevaluated in vitro using a 9.4 Tesla superconducting unit. The portal vein was cannulated and perfused by cooled Euro-Collins solution, and pig liver was removed and preserved in the solution. Five to 8 g of the liver was excised before and after preservation, then extracted by perchloric acid (PCA). In 1H-MRS of PCA extracted pig liver, large peaks of fatty acid disappeared, while peaks of the choline group from 3.2-3.3 ppm were clearly observed. Using high performance liquid chromatography (HPLC) and 31P (phosphorus)-MRS, the 3.23 ppm peak was determined as glycerophosphorylcholine (GPC), which diminished after preservation. The chronological change of GPC in PCA extracted pig liver was able to be observed by 1H-MRS. GPC peak may play a role as an indicator in evaluating preserved liver by 1H-MRS.     

Rhomboencephalitis caused by Listeria monocytogenes: a case studies with magnetic nuclear resonance

Central nervous system infections due to Listeria monocytogenes result in a variety of clinical syndromes ranging from meningitis to rhomboencephalitis. We report the case of a previously healthy patient with rhomboencephalitis in whom the CT scan was normal, while magnetic resonance imaging (MRI) confirmed the diagnosis. We review the literature and emphasize the value of MRI for timely diagnosis.     

Proton magnetic resonance spectroscopy in children with Sturge-Weber syndrome

Quantitative proton magnetic resonance spectroscopy was performed on six children with Sturge-Weber syndrome following gadolinium enhanced magnetic resonance imaging (MRI). MRI revealed only unilateral involvement in all cases. The mean concentration (mmol/kg wet weight) of the neuronal marker N-acetyl-aspartate was significantly reduced by 37% in the ipsilateral gadolinium enhanced volume of interest compared to a similarly placed contralateral volume of interest (5.39 +/- 1.70 [SD] vs 8.50 +/- 1.14, P < .005, two-tailed paired Student's t-test). Decreased N-acetyl-aspartate in the ipsilateral volume of interest was observed in all patients studied. No significant differences were found in the concentrations of creatine/phosphocreatine or choline compounds between the ipsilateral and contralateral volumes of interest. These findings give possible new insight into the pathophysiology of this disease and suggest that quantitative proton magnetic resonance spectroscopy may be useful for the early characterization and monitoring of neuronal dysfunction or loss in infants and children with Sturge-Weber syndrome.     

Proton magnetic resonance spectroscopy of linear nevus sebaceus syndrome

OBJECTIVE: The potential effect of ethnicity on the serum lipid profile and lipoprotein(a) [Lp(a)] was studied in a population with chronic spinal cord injury (SCI). STUDY DESIGN: The distribution and correlates of high density lipoprotein (HDL) cholesterol and Lp(a) were studied in a population of 600 subjects with chronic SCI. RESULTS: Mean +/- SEM serum HDL cholesterol was significantly higher in the African American group than in the white and Latino groups (47 +/- 1 vs 40 +/- 1 and 38 +/- 1 mg/dL, p < .0001, respectively). The African American group had a lower serum total to HDL cholesterol ratio than white and Latino groups (4.46 +/- .153 vs 5.18 +/- .168 and 5.40 +/- .140 mg/dL, p < .01, respectively). Mean serum Lp(a) levels were significantly higher in the African American group than in Latino or white groups (29 +/- 2 vs 18 +/- 1 and 15 +/- 1 mg/dL, p < .0001, respectively). Age, duration of SCI, and level and completeness of lesion had no significant effect on serum Lp(a) level. CONCLUSIONS: In a population with chronic SCI, those in the African American group had the highest serum HDL cholesterol concentrations, the lowest serum total to HDL cholesterol ratios, and elevated levels of serum Lp(a) compared with the Latino and white groups. In a population of individuals with chronic SCI, ethnicity was shown to have a major effect on serum lipids and may be used to assist in the determination of cardiovascular risk.     

Proton nuclear magnetic resonance sequential assignments and secondary structure of an immunoglobulin light chain-binding domain of protein L

The 1H NMR assignments have been made for the immunoglobulin (Ig) light chain-binding B1 domain of protein L from Peptostreptococcus magnus. The secondary structure elements and the global folding pattern were determined from nuclear Overhauser effects, backbone coupling constants, and slowly exchanging amide protons. The B1 domain was found to be folded into a globular unit of 61 amino acid residues, preceded by a 15 amino acid long disordered N-terminus. The folded portion of the molecule contains a four-stranded beta-sheet spanned by a central alpha-helix. The fold is similar to the IgG-binding domains of streptococcal protein G, despite the fact that the binding sites on immunoglobulins for the two proteins are different; protein G binds IgG through the constant (Fc) part of the heavy chain, whereas protein L has affinity for the variable domain of Ig light chains.     

Silicon-29 nuclear magnetic resonance spectroscopy detection limits

We show that an unmodified, commercially available high-field (17.61T) NMR spectrometer using the DEPT pulse sequence is capable of detecting silicon-containing species down to concentrations of 150 ng/mL (150 ppb) per spin site. This is in the range given for the concentration of silicon in the blood of silicone breast implant recipients, as determined by ICP analysis, and demonstrates that, contrary to the view expressed in the literature, in theory 29Si NMR may be sufficiently sensitive to be of use in determining the nature of the silicon-containing species present. A summary of the factors affecting the detection limits in NMR spectroscopy is given.     

原子核磁共振显微检测芯片的磁路设计

基于磁路设计理论首先设计了一种适用于原子核磁共振显微检测芯片的永磁磁路;然后根据磁路磁通折射定理和基尔霍夫第一定律对设计的磁路模型进行理论分析,提出了单一匀场环磁路性能优化方法;最后利用有限元方法分别计算了优化前的磁路、单一匀场环优化后磁路和传统的双匀场环优化后磁路.计算结果表明:相比优化前和采用传统的双匀场环优化后的磁路,采用单一匀场环优化后的磁路其性能最优,工作区域内磁场强度和均匀度都得到了极大的提高,磁场强度达到0.703 544 T,工作区域内磁场均匀度为14×10-6.因此所设计的磁路能够较好地满足原子核磁共振显微检测芯片的需求.     

Computerized tomography versus nuclear magnetic resonance in acute pancreatitis

The aim of the study was to compare Computed Tomography (CT) and Nuclear Magnetic Resonance (MR) scan's diagnostic reliability in acute pancreatitis (AP). During a 44-month period 21 patients with a clinical and laboratory diagnosis of AP were submitted to CT and MR study. The scans were evaluated according to pancreatitis degree and presence and rate of necrosis. Pancreatitis degree was assessed using Balthazar's grading for CT scans; a similar classification was used for MR scans. Thirteen patients had oedematous pancreatitis and 8 necrotic pancreatitis. Necrosis was diagnosed intraoperatively or in non operated patients with CT scan. MR staging was identical to that of the CT ones except for 2 patients who were grade E at CT and grade D at MR. MR identified necrosis in all 8 patients with necrotic AP whereas CT diagnosed only 5 patients properly since 3 scans were performed without contrast medium infusion because of renal failure. MR proved to be a valid alternative in AP diagnosis: it provide the same diagnostic and prognostic information as CT and does not need contrast infusion, which makes it preferable to CT in the follow-up of severe AP evolution.     

Lecithin translational diffusion studied by pulsed nuclear magnetic resonance

The translational diffusion coefficient of egg yolk and dilauroyl lecithin in optically isotropic phases containing sodium cholate has been measured using the pulsed NMR magnetic field gradient method. After a correction for geometrical factors the measured diffusion coefficient is found to agree well with previous determinations in phospholipid systems. The experimental data imply that the cubic mesophase of the lecithin-sodium cholate-water system contains continuous lipid aggregates. A possible model of the arrangement of the different amphiphile molecules in the cubic phase is discussed.     

卸荷岩体细观损伤演化的核磁共振测试

为研究卸荷岩体内部孔隙结构的细观损伤演化特征,以大理岩为岩样,分别进行初始围压为10、20和30 MPa,不同卸荷围压量的常规三轴卸荷试验和核磁共振测试实验,获得卸荷岩体的应力-应变曲线、横向弛豫时间T₂分布、孔隙度及核磁共振成像图像.随着卸荷围压比的增大,岩石由弹性变形转化为塑性变形,岩样内小孔隙的孔径增大,大孔隙的数量增多且孔径增大;卸荷围压比低于90%,岩体损伤主要由孔隙数量的增多引起,卸荷围压比高于90%,损伤由孔隙数量和孔径均急剧增大引起;岩样的孔隙度随着卸荷围压比的增大而增大,且增速越来越快;核磁共振图像直观地反映卸荷岩体内部孔隙数量、孔径及结构变化情况.