Missed lung cancer on chest radiography and computed tomography: imaging and medicolegal issues

The solvent and temperature dependence of the rate constant for spin echo dephasing, 1/Tm, for 0.2 to 1.2 mM glassy solutions of chromyl bis(1-hydroxy-cyclohexanecarboxylic acid), CrO(HCA)-2; aquo vanadyl ion, VO2+ (aq), and vanadyl bis(trifluoroacetylacetonate), VO(tfac)2 were examined. At low temperatures where 1/T1 < 1/Tm, 1/Tm in 1:1 H2O:glycerol is dominated by solvent protons. At low temperature 1/Tm increases in the order 1:1 H2O:glycerol or 9:1 CF3CH2OH:ethyleneglycol (no methyl groups) < 9:1 i-PrOH:MeOH (hindered methyl groups) < 9:1 n-PrOH:MeOH (less hindered methyl groups). This solvent dependence of 1/Tm is similar to that observed for nitroxyl radicals, which indicates that the effect of solvent methyl groups on spin-echo dephasing at low temperature is quite general. At higher temperatures the echo dephasing is dominated by spin-lattice relaxation and is concentration dependent. As the glass softens, echo dephasing is dominated by the onset of molecular tumbling.     

Softening temperature of lyophilized bovine serum albumin and gamma-globulin as measured by spin-spin relaxation time of protein protons

We investigated the usefulness of the spin-spin relaxation time (T2) of protein protons as a probe for evaluating the molecular flexibility of freeze-dried protein formulations. It is proposed that the microscopic softening temperature determined from changes in the T2 of protein protons (Ts(T2)) is an important characteristic of freeze-dried protein formulations, the glass transition temperature (Tg) of which is generally difficult to determine by differential scanning calorimetry. We determined the molecular flexibility of lyophilized bovine serum albumin (BSA) and bovine gamma-globulin (BGG) by measuring the T2 of protein and water protons as well as the spin-lattice relaxation time (T1) of the latter as a function of temperature. The flexibility of freeze-dried BSA and BGG cakes markedly varied at temperatures above and below the Ts(T2), affecting the stability of the proteins. The denaturation and subsequent aggregation of lyophilized BSA and BGG cakes with a relatively high water content was enhanced in the softened state at temperatures above the Ts(T2). Lyophilized cakes with an extremely low water content were significantly denatured, even in the unsoftened state at temperatures below the Ts(T2), probably due to the thermodynamically unstable structures of protein molecules generated by a loss of structural water.     

微波消解技术应用于难分解贵金属化合物的分析

提出了微波密闭快速消解难分解的KAu(CN)2,KAu(CN)4,Pt(NH3)2(NO2)2,K2[Pt(NO2)4],Pt(NH3)2Cl2,Pt(NH3)4Cl2,(NH4)2PtCl6,K2PtCl4,Pt(C5H7O2)2等化合物的方法。比较了微波密闭消解法与传统分解法的条件;采用精密电化学滴定法分析了Au和Pt的含量,并与传统分析方法BS5658法(H2SO4发烟重量法)、火试金法和湿法重量法进行了结果对照。结果表明:以HCl-H2O2,HCl-HNO3分别为Au和Pt类化合物的消解试剂,于优     

DNA interactions of a novel platinum drug, cis-[PtCl(NH3)2(N7-acyclovir)]+

We synthesized a novel platinum drug, cis-[PtCl(NH3)2(N7-ACV)]+, in which ACV is the antiviral drug acyclovir [a deoxyriboguanosine analogue, 9-(2-hydroxyethoxymethyl)guanine]. This new compound exhibits antiviral efficacy in vitro and exhibits an antitumor activity profile different from that of cisplatin [Metal-Based Drugs 2:249-256 (1995)]. To contribute to understanding the mechanisms underlying biological activity of this new compound, we studied modifications of natural and synthetic DNAs in cell-free media by cis-[PtCl(NH3)2(N7-ACV)]+ by various biochemical and biophysical methods. The results indicated that the major DNA adduct of cis-[PtCl(NH3)2(N7-ACV)]+ was a stable monofunctional adduct at guanine residues. In contrast to DNA adducts of other monodentate and clinically ineffective platinum(II) compounds, the adducts of cis-[PtCl(NH3)2(N7-ACV)]+ terminated in vitro DNA and RNA synthesis. In addition, although DNA adducts of cis-[PtCl(NH3)2(N7-ACV)]+ and cisplatin were different, some properties of DNA modified by either compound were qualitatively similar. Such similarities were not noticed if DNA modifications by other ineffective monofunctional platinum(II) complexes were investigated. Thus, the DNA binding mode of monofunctional cis-[PtCl(NH3)2(N7-ACV)]+ was different from that of other monofunctional but ineffective platinum(II) complexes. It has been suggested that the unique capability of cis-[PtCl(NH3)2(N7-ACV)]+ to modify DNA may be relevant to a distinct antitumor efficiency of this novel drug in comparison with cisplatin. It also has been suggested that at least some aspects of DNA interactions of cis-[PtCl(NH3)2(ACV)]+ revealed in the current study could be exploited in the search for and development of new antiviral platinum complexes containing, as a part of the coordination sphere, antiviral nucleosides.     

Neomycin, spermine and hexaamminecobalt (III) share common structural motifs in converting B- to A-DNA

The (dG)n.(dC)n-containing 34mer DNA duplex [d(A2G15C15T2)]2 can be effectively converted from the B-DNA to the A-DNA conformation by neomycin, spermine and Co(NH3)6(3+). Conversion is demonstrated by a characteristic red shift in the circular dichroism spectra and dramatic NMR spectral changes in chemical shifts. Additional support comes from the substantially stronger CH6/GH8-H3'NOE intensities of the ligand-DNA complexes than those from the native DNA duplex. Such changes are consistent with a deoxyribose pucker transition from the predominate C2'-endo (S-type) to the C3'-endo (N-type). The changes for all three ligand-DNA complexes are identical, suggesting that those three complex cations share common structural motifs for the B- to A-DNA conversion. The A-DNA structure of the 4:1 complex of Co(NH3)6(3+)/d(ACCCGCGGGT) has been analyzed by NOE-restrained refinement. The structural basis of the transition may be related to the closeness of the two negatively charged sugar-phosphate backbones along the major groove in A-DNA, which can be effectively neutralized by the multivalent positively charged amine functions of these ligands. In addition, ligands like spermine or Co(NH3)6(3+) can adhere to guanine bases in the deep major groove of the double helix, as is evident from the significant direct NOE cross-peaks from the protons of Co(NH3)6(3+) to GH8, GH1 (imino) and CH4 (amino) protons. Our results point to future directions in preparing more potent derivatives of Co(NH3)6(3+) for RNA binding or the induction of A-DNA.     

Characterization of ligands of a high-affinity metal-binding site in the latent chloroplast F1-ATPase by EPR spectroscopy of bound VO2+

Vanadyl, (V = O)2+, is able to substitute for Mg2+ as a cofactor for ATPase activity catalyzed by the chloroplast F1-ATPase (CF1). Mg2+-dependent ATPase activity was also observed with CF1 that contained VO(2+)-ATP bound specifically to the noncatalytic N2 site. Modulation of the Mg(2+)-ATPase activity induced by VO2+ bound at this site indicates that the metal bound to the noncatalytic site affects catalytic activity. When CF1 is depleted of nucleotides from all but the N1 site, a single Mg2+ remains bound at a site designated M1. Addition of VO2+ to the depleted protein gives rise to an EPR spectrum characteristic of a CF1-bound VO2+ species. The binding curve of the VO2+ complex to latent, nucleotide-depleted CF1 was determined by the integrated intensities of the -5/2 parallel peak in the EPR spectrum as calibrated using atomic absorption spectroscopy. Under these conditions, VO2+ binds cooperatively to approximately two sites designated M2 and M3. Three-pulse ESEEM spectra of the CF1-VO2+ complex contain two intense modulations with frequencies and field-dependent behavior that show that they are from a directly coordinated 14N nucleus. Analysis of the bound VO2+ by ENDOR spectroscopy revealed the presence of a single group of protons associated with an equatorial amino or water ligand that is exchangeable with solvent. Using the additivity relation for hyperfine coupling, the most probable set of equatorial ligands to the VO2+ bound to CF1 under these conditions consists of one lysine nitrogen, two carboxyl oxygens from aspartate or glutamate, and one water.     

偏钒酸铵在空气中热分解产物形貌的演变

以偏钒酸铵(NH_4VO_3)在空气中热分解的热重-差热(TG-DSC)分析为依据,利用X射线衍射仪(XRD)和扫描电镜(SEM)分析了偏钒酸铵在空气中热分解最终产物的物相和偏钒酸铵在空气中升温到DSC曲线不同拐点温度分解产物的形貌。研究发现,偏钒酸铵在空气中热分解有两个阶段,第一阶段出现了中间相(NH_4)_2O·2V_2O_5,第二阶段出现了热分解产物由无定形状态转变成晶体的过程。偏钒酸铵在空气中不同阶段下热分解产物的形貌基本上是不规则的片状,但是最终产物V_2O_5的厚度较均匀。     

Structure and intramodular dynamics of the amino-terminal LIM domain from quail cysteine- and glycine-rich protein CRP2

Members of the cysteine and glycine-rich protein (CRP) family (CRP1, CRP2, and CRP3) contain two zinc-binding LIM domains, LIM1 and LIM2, and are implicated in diverse cellular processes linked to differentiation, growth control and pathogenesis. The solution structure of an 81-amino acid recombinant peptide encompassing the amino-terminal LIM1 domain of quail CRP2 has been determined by 2D and 3D homo- and heteronuclear NMR spectroscopy. The LIM1 domain consists of two zinc binding sites of the CCHC and the CCCC type, respectively, which both contain two orthogonally arranged antiparallel beta-sheets and which are packed together by a hydrophobic core composed of residues from the zinc finger loop regions. The CCCC zinc finger is followed by a short alpha-helical stretch. The structural analysis revealed that the global fold of LIM1 closely resembles the recently determined solution structures of the carboxyl-terminal LIM2 domains of quail CRP2 and chicken CRP1, and that LIM1 and LIM2 are independently folded structural and presumably functional domains of CRP proteins. To explore the dynamical properties of CRP proteins, we have used 15N relaxation values (T1, T2, and nuclear Overhauser effect (NOE) to describe the dynamical behavior of a LIM domain. A model-free analysis revealed local variations in mobility along the backbone of the quail CRP2 LIM1 motif. Slow motions are evident in turn regions located between the various antiparallel beta-sheets or between their strands. By use of an extended motional model, fast backbone motions were detected for backbone amide NH groups of hydrophobic residues located in the core region of the LIM1 domain. These findings point to a flexible hydrophobic core in the LIM1 domain allowing residual relative mobility of the two zinc fingers, which might be important to optimize the LIM1 interface for interaction with its physiological target molecule(s) and to compensate enthalpically for the entropy loss upon binding.     

Cholecystokinin B receptors in the periaqueductal gray potentiate defensive rage behavior elicited from the medial hypothalamus of the cat

The sequence specificity of ten cisplatin analogues was examined in intact human cells. Six of these compounds have anti-tumour activity. The sequence selectivity was investigated using a Taq DNA polymerase/linear amplification assay on damaged DNA extracted from treated cells. Cisplatin and tetraplatin(IV) produced strong damage and DACH RR(II) and cis-[Pt(II)Cl,2(iPrNH2)2] weak DNA damage in intact HeLa cells. The sequence selectivity of tetraplatin(IV) in intact human cells was very similar to that of cisplatin and favored runs of consecutive purines, especially consecutive guanines. The compounds transplatin, carboplatin, cis-[PtCl(NH3)2(C8H17.NH2)], cis-[PtCl2(iPentNH2)2], cis-[PtCl2(C6H11NH2)2, DACH SS(II) and CHIP(IV) did not significantly damage DNA in cells. It was concluded that the interactions of these cisplatin analogues with DNA in human cells were strongly influenced by their ability to damage purified DNA.     

A review of the recent advances in magnetic resonance imaging in the assessment of osteoporosis

Osteoporosis is a common metabolic disorder with considerable associated morbidity and mortality. The loss of bone mineral integrity and the resultant occurrence of atraumatic fractures are typically symptomatic of the disease. Currently skeletal status is commonly assessed using non-invasive conventional radiography and scintigraphy as well as densitometric techniques such as quantitative computed tomography and dual-energy X-ray absorptiometry. But, apart from gross bone mineral density, the fine structure of trabecular bone also plays an important role in defining the biomechanical competence of the skeleton. Recently attention has been focused on deriving measures that provide information about not only trabecular bone density but also microstructure. Magnetic resonance imaging (MRI) is one such new technique which potentially may provide information pertaining to bone density and structure as well as to occult fracture detection. Cortical bone produces a signal void in MR images, due to the fact that it contains very few mobile protons that give rise to a signal in MRI; also the MR relaxation time T2 of these protons is very short which produces a very fast decay of the MR signal during image acquisition. However, the trabecular bone network affects the MR properties of bone marrow. The difference in the magnetic properties of trabecular bone and bone marrow generates local imperfections in the magnetic field. The MR signal from bone marrow is modified due to these imperfections and the MR relaxation time T2 of marrow is shortened. The extent of relaxation time shortening and hence loss of signal intensity is proportional to the density of trabecular bone and marrow interfaces and their spatial architecture. Recent investigation in this area include studies aimed at quantifying marrow relaxation times and establishing their relationship to trabecular bone density and structure. In addition, with advances in imaging software and hardware, MR images at in-plane resolutions of 78-200 microns may be obtained. The trabecular bone structure is clearly revealed in such images and studies aimed at the development of high-resolution MRI techniques combined with quantitative image analysis techniques are currently under way. These potentially useful techniques for assessing osteoporosis and predicting fracture risk are reviewed in this paper.     

1H MAS NMR spectroscopy of chemically modified silica gels: a fast method to characterize stationary interphases for chromatography

Chemically modified silica gels used as stationary phases in chromatography have been investigated by means of solid-state 1H magic angle spinning (MAS) NMR spectroscopy. Since the organosilanes are bonded to the surface of the silica gel, their protons are diluted and possess a higher mobility in comparison to protons in pure organic solids. Thereby the usually strong homonuclear dipole-dipole interactions among the protons are reduced and it is possible to obtain well-resolved 1H NMR spectra of the organic interphases with MAS-only techniques. Effects of temperature and magnetic field strength on the resolution of the spectra are examined as well as the dependence of T1 and T1pH relaxation times on temperature and spinning speed.     

Glyoxalase I (GLO I, EC 4.4.1.5) polymorphism in hemolysates and bloodstains

Oxidized and reduced forms of high-potential iron-sulfur protein (HiPIP) from the purple non-sulfur photosynthetic bacterium Rhodoferax fermentans have been characterized using 1H-NMR spectroscopy. Pairwise and sequence-specific assignments of hyperfine-shifted 1H-NMR signals to protons of cysteine residues bound to the [4Fe-4S]3+/2+ cluster have been performed using one-dimensional NOE and exchange spectroscopy experiments. 1H-NMR hyperfine shifts and relaxation rates of cluster-bound Cys beta-CH2 protons indicate that in the [4Fe-4S]3+ cluster one iron ion can be formally described as Fe(III), while electron density corresponding to one electron is unevenly delocalized onto the remaining three iron ions. This delocalization is effected by means of two different electronic distributions interconverting rapidly on the NMR time scale. The mechanism of paramagnetic proton relaxation, studied by analyzing longitudinal relaxation rates of Cys beta-CH2 protons in HiPIPs from six different sources as a function of the Fe-S-C beta-C alpha dihedral angle, indicate that the major contribution is due to a dipolar metal-centered mechanism, with a non-negligible contribution from a ligand-centered dipolar mechanism which involves the 3p orbital of the Cys sulfur atom. A semi-quantitative tool for extracting structural information from relaxation time measurements is proposed.     

Structural studies by high-field NMR spectroscopy of a binary-addressed complementary oligonucleotide system juxtaposing pyrene and perfluoro-azide units

Recently, a new approach has been proposed to improve the site-specificity and efficiency of the modification of nucleic acid target sequences, the binary system of complementary-addressing nucleic acid sequences. The binary system comprises two oligonucleotides, one modified with a photosensitizing group and the other with a photoreactive group. The sites of chemical modification are arranged to bring the two chemical functions close enough together in space to allow efficient energy transfer from the photo-excited photosensitizer to an arylazide moiety which expels N2 to form a nitrene which subsequently covalently labels the target nucleic acid. Structural analysis performed by high-resolution 2D NMR spectroscopy (400 MHz and 600 MHz) are reported for the model binary system 1:2:3, where 1 is the target 12-mer pdGTATCAGTTTCT, 2 is a photoactivatable fluoroazide derivative dAGAAACp-L-Az and 3 is the photosensitizer derivative Pyr-pdTGATAC (here: Az is the p-azidotetrafluorobenzyl group, Pyr the pyrenyl-1-methylamino group, L a linker group). The assignment of oligonucleotide and modifying group protons was performed using 1H COSY, TOCSY and NOESY experiments. Comprehensive analysis of 1H NOESY spectra of 1:2:3 showed that terminal fragments of the complex [5'p-1T-2G-3A-4T-], [-21A-22T-23A-24C], [-8T-9T-10T-11C-12T] and [13A-14G-15A-15A-17A-18C-] gave a continuous set of intra- and inter-nucleotide interactions, typical of regular double-stranded B-DNA. In contrast, the central region of the complex composed of 5C, 6A, 7G, 19T and 20G nucleotide residues, nearest the Pyr and Az groups, was found to be distorted. Thus some signals from aromatic and/or sugar-ring protons of the above nucleotide residues were extremely broadened or almost absent. Moreover, some intra- and/or inter-nucleotide interactions, typical of the regular DNA duplex, were not detected for the [-5C-6A-7G-] and [-19T-20G-] regions of the tandem system. Instead of that, some cross-peaks of low-intensity between the H2 proton of the Pyr group and 7G(H1'), 7G(H2'/H2"), 7G(H3'), 4T(H2"), 4T(H4') and 4T(H5'/H5") were observed. Additional 1H -1H NOE-interactions between methylene protons of the linker group L and some sugar ring protons of 18C nucleotide residue were detected. A preliminary structural model, constructed using proton-proton distances between Pyr and the DNA and Az-L and DNA obtained from a 1H NOESY experiment at 300 ms mixing time as constraints for the refinement of the structure, displayed significant distortion from B-DNA of the double-stranded helix in the middle of the complex, (-5C-6A-7G, -18C-19T-20G-). The Pyr group was located in what remains of the minor groove near 4T, 5C, 6A and 7G and the centroid of the azide ring less than 9A degrees from the centroid of the ring system of Pyr group.     

Nuclear relaxation and gelation study of the interaction of organophosphates with human normal and sickle hemoglobins. In vitro gelation of sickle oxyhemoglobin in the presence of inositol hexaphosphate

31P relaxation studies reveal a 3-fold enhancement of the longitudinal relaxation rate of both phosphoryl groups of hemoglobin-bound 2,3-bisphosphoglycerate upon conversion of methemoglobin to fluoromethemoglobin presumably due to an order of magnitude increase in the electron spin relaxation time. The enhancement of the longitudinal components of 31P relaxation (T(-1)1pr) upon binding to hemoglobin is not exchange-limited, since it is more than an order of magnitude smaller than the effect observed on the transverse components (T(-1)2pr). From the observed paramagnetic component, T(-1)1M, of the bound state relaxation rate of 2,3-bisphosphoglycerate, using the correlation time tau s obtained from the frequency dependence of water proton relaxation, we obtained an NMR root mean sixth distance from the four heme iron atoms to each of the 31P nuclei of 24 +/- 1 A. This is in excellent agreement with the x-ray crystallographic determination of this distance of (25 +/- 1) A in the 2,3-bisphosphoglycerate-deoxyhemoglobin complex, indicating that the spatial disposition of the allosteric site in the deoxy and oxy conformations of hemoglobin relative to the various heme irons may be the same, and that the same protein groups may be involved in binding 2,3-bisphosphoglycerate to the two forms of hemoglobin. Water proton relaxation studies reveal the existence of different conformational states of methemoglobins with 2,3-bisphosphoglycerate and inositol hexaphosphate. Inositol hexaphosphate alters the conformation to a strained (T) state with deoxy-like quaternary and tertiary globin structure as indicated by the finding that equimolar amounts of inositol heasphosphate induce gelation in a 4 mM sickle methemoglobin solution at temperatures greater than or equal 24 degrees. More interestingly, oxyhemoglobin S shows an identical thermodynamically reversible gelation behavior, with the same transition temperature (24 degrees), arguing against a mutual coupling of the protein conformation and the heme spin state in functional ferrohemoglobins. High ionic strengths (approximately 1 M) and pH values above neutrality block inositol hexaphosphate induced gelation of sickle met- and oxyhemoglobins. Unlike inositol hexaphosphate, the presence of saturating amounts of 2,3-bisphosphoglycerate does not promote gelation of a 4 mM met- or oxyhemoglobin S solution.     

Solution NMR characterization of hydrogen bonds in a protein by indirect measurement of deuterium quadrupole couplings

Hydrogen bonds stabilize protein and nucleic acid structure, but little direct spectroscopic data have been available for characterizing these critical interactions in biological macromolecules. It is demonstrated that the electric field gradient at the nucleus of an amide hydrogen can be determined residue-specific by measurement of 15N NMR relaxation times in proteins dissolved in D2O, and uniformly enriched with 13C and 15N. In D2O, all backbone amide protons can be exchanged with solvent deuterons, and the T1 relaxation rate of a deuteron is dominated by its quadrupole coupling constant (QCC), which is directly proportional to the electric field gradient at the nucleus. 2HN T1 relaxation can be measured quantitatively through its effect on the T2 relaxation of its directly attached 15N. QCC values calculated from 2HN T1 and previously reported spectral densities correlate with the inverse cube of the X-ray crystal structure-derived hydrogen bond lengths: QCC = 228 + Sigmai 130 cos alphai/ri3 kHz, where alpha is the N-H...Oi angle and r is the backbone-backbone (N-)H...Oi(=C) hydrogen bond distance in angstroms.     

Structure of gene 5 protein-oligodeoxynucleotide complexes as determined by 1H, 19F, and 31P nuclear magnetic resonance

1H nuclear magnetic resonance (NMR) spectra at 270 MHz of gene 5 protein from bacteriophage fd and its complexes with tetra- and octadeoxynucleotides show that approximately 12 of the 37 aromatic protons of the protein undergo upfield shifts upon nucleotide binding. In the complex with d(pT)8, the upfield shifts of the aromatic protons average approximately 0.3 ppm, while in the d(pA)8 complex the same resonances (assigned to tyrosyl protons) shift upfield approximately 0.8 ppm. These are interpreted as ring current shifts induced by stacking of the phenyl rings of three of the five tyrosyl residues with the bases of the nucleotides. 19FNMR of m-fluorotyrosyl gene 5 protein shows five separate resonances: two downfield from m-fluorotyrosine corresponding to "buried" tyrosyls and three near m-fluorotyrosine corresponding to "surface" tyrosyls. The latter (assigned to Tyr-26, -41, and -56, shown by chemical modification to be exposed to solvent) move upfield on nucleotide binding. The downfield 19F resonances are unaffected. Thus the aromatic protons shifted upfield on nucleotide binding appear to be those of Tyr-26, -41, and -56. In contrast to tetra-, octanucleotide binding to gene 5 protein induces large changes in the 1H resonances of the -CH3 groups of the Val, Leu, and Ile side chains. These may reflect conformational changes induced by protein-protein interactions between two monomers bound to the octanucleotide. 1H resonances of the epsilon-CH2 groups of the lysyl residues in the protein and the complexes with nucleotides are narrow with long T2 values, suggesting considerable rotational motion. Thus epilson-NH3+-phosphate interactions, if they occur, are on the surface of the complex and allow the epsilon-CH2 groups to retain considerable rotational freedom. 31P NMR of the bound nucleotides shows large decreases in T1 for the 3'-5' diesters, but little chemical shift suggesting no unusual distortion of the nucleotide backbone on binding to gene 5 protein. A three-dimensional model of a gene 5 protein-octanucleotide complex has been built based on predictions of the secondary structure from the amino acid sequence (87 AA) and tertiary folding dictated by known chemical and NMR features of the complex.     

Orientation of the heme vinyl groups in the hydrogen sulfide-binding hemoglobin I from Lucina pectinata

Hemoglobin I (HbI) from the claim Lucina pectinata is a unique heme protein that binds and transfers hydrogen sulfide (H2S) to a symbiotic bacteria. The metcyano, metaquo, carbon monoxy, oxy, and deoxy complexes of HbI were studies by resonance Raman (RR) spectroscopy, and the metacyano and carbon monoxy complexes were also studied by 1H-NMR. The results indicate a unique orientation of the heme 2-vinyl group relative to other heme proteins. The RR spectra of the HbICO, metHbICN, metHbIH2O, HbIO2 and deoxyHbI heme derivatives show a band at 1621 cm-1 and a shoulder at 1626 cm-1, indicative of an out-of-plane position for one of the vinyls relative to the other one. Spin-lattice relaxation properties of protons in the metHbICN complex also suggest a unique orientation for the heme 2-vinyl group of HbI. The longitudinal relaxation time (T1) for the 2-H alpha, 2-H beta c, and H beta t protons are 120 ms, 115 ms, and 135 ms, respectively. The data from both techniques suggest an out-of-plane and trans-oriented 2-vinyl group, and an in-plane and cis-oriented 4-vinyl group for the low-spin complexes of HbI. These results imply that the electron withdrawing character of the out-of-plane vinyl group contributes to the stability of the heme Fe+3 oxidation state, facilitates the binding of the H2S ligand, and promotes the stability of this ferric H2S complex.     

Intracellular application of calmidazolium increases Ca2+ current through activation of protein kinase A in cultured vascular smooth muscle cells

This study compared markers of the metabolic processes occurring in male and female adolescent triathletes from two age groups (over 15 years of age [O15] and under 15 years of age [U15]) during a laboratory based duathlon. Participants were tested on three separate occasions; two peak VO2 tests on a treadmill and cycle ergometer, and a third session involved a simulated duathlon (2 km run, 12 km ride and 4 km run for the O15 group or 1 km run, 8 km ride and 2 km run for the U15). Data collection included performance speed, cardiorespiratory responses and blood borne markers of exercise metabolism. The performance speeds selected by the two age groups did not differ. The mean relative percentage of VO2peak at which subjects participated were 79+/-3, 77+/-4%, for the O15 males and females, and 71+/-5 and 82+/-2%, for the U15 males and females, respectively. While the plasma metabolites of ammonia [NH3] and lactate [La] were not different between age groups and sex (p>0.05) there were however, higher concentrations recorded during the cycling phase when compared with the running phases (p < 0.05). The respective mean concentrations for NH3 and La were 80.5+/-5.6 microM, and 4.9+/-0.3 microM for cycling, and 56.3+/-2.7 microM, and 2.7+/-0.2 microM for the combined running phases.     

Structural characterization of the O-antigenic polysaccharide of Escherichia coli serotype 017 lipopolysaccharide

Transverse nuclear magnetic relaxation and self-diffusion of water were measured in hydrated collagen II. Self-diffusion measurements were conducted by pulsed field gradient NMR (PFG NMR) and weighting of the different species in the signal by variable T2 relaxation in the experiment. Two fractions of water protons were detected, one with a short T2 value but high diffusivity and one with a long T2 value and low, completely restricted diffusion. The distance of the diffusion barriers was determined to be 2.3 microns. Possible reasons for the restriction in the movement of the water molecules in comparison with structural models of collagen II are discussed.     

15N NMR relaxation studies of calcium-loaded parvalbumin show tight dynamics compared to those of other EF-hand proteins

Dynamics of the rat alpha-parvalbumin calcium-loaded form have been determined by measurement of 15N nuclear relaxation using proton-detected heteronuclear NMR spectroscopy. The relaxation data were analyzed using spectral density functions and the Lipari-Szabo formalism. The major dynamic features for the rat alpha-parvalbumin calcium-loaded form are (1) the extreme rigidity of the helix-loop-helix EF-hand motifs and the linker segment connecting them, (2) the N and C termini of the protein being restricted in their mobility, (3) a conformational exchange occurring at the kink of helix D, and (4) the residue at relative position 2 in the Ca2+-binding sites having an enhanced mobility. Comparison of the Ca2+-binding EF-hand domains of alpha-parvalbumin-Ca2+, calbindin-Ca2+, and calmodulin-Ca2+ shows that parvalbumin is probably the most rigid of the EF-hand proteins. It also illustrates the dynamical properties which are conserved in the EF-hand domains from different members of this superfamily: (1) a tendency toward higher mobility of NH vectors at relative position 2 in the Ca2+-binding loop, (2) a restricted mobility for the other residues in the binding loop, and (3) an overall rigidity for the helices of EF-hand motifs. The differences in mobility between parvalbumin and the two EF-hand proteins occur mainly at the linker connecting the pair of EF hands and also at the C terminus of the last helix. In parvalbumin-Ca2+, these two regions are characterized by a pronounced rigidity compared to the corresponding more mobile regions in calbindin-Ca2+ and calmodulin-Ca2+.