HRV biofeedback for pediatric irritable bowel syndrome and functional abdominal pain: a clinical replication series.

Irritable bowel syndrome (IBS) and Functional Abdominal Pain (FAP) are among the most commonly reported Functional Gastrointestinal Disorders. Both have been associated with varying autonomic dysregulation. Heart Rate Variability Biofeedback (HRVB) has recently begun to show efficacy in the treatment of both IBS and FAP.

Direct voltammetric investigation of the electrochemical properties of human hemoglobin: relevance to physiological redox chemistry.

Voltammetric measurements on solutions of human hemoglobin using gold electrodes modified with omega-hydroxyalkanethiols have yielded the first direct measure of the reorganization energy of the protein. The value obtained based on extrapolation of the experimentally measured currents, 0.76 eV, is independent of pH (i.

Voltammetric probes of cytochrome electroreactivity: the effect of the protein matrix on outer-sphere reorganization energy and electronic coupling probed through comparisons with the behavior of porphyrin complexes.

Using surface-modified electrodes composed of omega-hydroxyalkanethiols, an experimentally based value for the inner-sphere reorganization energy of the bis(imidazole)iron porphyrin system has been obtained by examining the solvent dependence of the reorganization energy of bis(N-methylimidazole)meso-tetraphenyl iron porphyrin. The value obtained (0.41 +/- 0.

NMR studies of the structure and dynamics of peptide E, an endogenous opioid peptide that binds with high affinity to multiple opioid receptor subtypes.

Structural and dynamic properties of opioid peptide E have been examined in an sodium dodecyl sulfate (SDS) micelle. Structural and dynamic studies both indicate that this peptide exhibits greater segmental mobility than typical structured proteins. An nmr structural analysis of adrenal peptide E in SDS micelles indicated the presence of two well-defined beta-turns, one at the N-terminus encompassing residues 3 to 6, and the second in the region between residues 15 and 18.

The origin of differences in the physical properties of the equilibrium forms of cytochrome b5 revealed through high-resolution NMR structures and backbone dynamic analyses.

On the basis of a comparison of high-resolution solution structures calculated for both equilibrium forms of rat ferrocytochrome b5, differences in reduction potential and thermodyanmic stability have been characterized in terms of significant structural and dynamic differences between the two forms. The dominant difference between A and B conformations has long been known to be due to a 180 degrees rotation of the heme in the binding pocket about an axis defined by the alpha- and gamma-meso carbons, however, the B form has not been structurally characterized until now. The most significant differences observed between the two forms were the presence of a hydrogen bond between the 7-propionate and the S64 amide in the A form but not the B form and surprisingly a displacement of the heme out of the binding pocket by 0.

Sulfur K-edge x-ray absorption spectroscopy: a spectroscopic tool to examine the redox state of S-containing metabolites in vivo.

The sulfur K-edge x-ray absorption spectra for the amino acids cysteine and methionine and their corresponding oxidized forms cystine and methionine sulfoxide are presented. Distinct differences in the shape of the edge and the inflection point energy for cysteine and cystine are observed. For methionine sulfoxide the inflection point energy is 2.

Optimized gene synthesis, high level expression, isotopic enrichment, and refolding of human interleukin-5.

Structural studies on soluble proteins using nuclear magnetic resonance (NMR) spectroscopy and other structural methods in general require large quantities of isotopically enriched proteins. Human interleukin-5 is a disulfide-linked homodimeric cytokine implicated in asthmatic response. The development of a high yield overexpression system for human interleukin-5 is an important prerequisite to using modern multidimensional NMR in the characterization of the solution structure of the protein and to characterize interactions with a soluble receptor domain.

Effect of axial ligand plane reorientation on electronic and electrochemical properties observed in the A67V mutant of rat cytochrome b5.

Mutational studies directed at evaluating the effect of the axial ligand plane orientation on electrochemical properties of cytochrome b5 have been performed. As described in the previous paper, structural consequences of one of these mutations, the A67V mutation, have been evaluated using NMR solution methods. The lack of large shifts relative to the wild-type protein in both the imidazole Ndelta nitrogen and proton resonances of the H63 imidazole ring indicates that the hydrogen bond between the carbonyl of F58 and the imidazole ring of H63 remains intact in this mutant.

Characterization of a site-directed mutant of cytochrome b5 designed to alter axial imidazole ligand plane orientation.

Mutants of cytochrome b5 were designed to achieve reorientation of individual axial imidazole ligands. The orientation of the axial ligand planes is thought to modulate the reduction potential of bis(imidazole) axially ligated heme proteins. The A67V mutation achieved this goal through the substitution of a bulkier, hydrophobic ligand for a residue, in the sterically hindered hydrophobic heme binding pocket.

1H, 13C and 15N NMR assignments and secondary structure of the paramagnetic form of rat cytochrome b5.

Modern multidimensional double- and triple-resonance NMR methods have been applied to assign the backbone and side-chain 13C resonances for both equilibrium conformers of the paramagnetic form of rat liver microsomal cytochrome b5. The assignment of backbone 13C resonances was used to confirm previous 1H and 15N resonance assignments [Guiles, R.D.

Pseudocontact shifts used in the restraint of the solution structures of electron transfer complexes.

The geometry of the ferricytochrome b5-ferricytochrome c complex has been analysed using long-range interprotein paramagnetic dipolar shifts. Heteronuclear filtered NMR spectra of samples containing 15N-labelled cytochrome b5 in complex with unlabelled cytochrome c allowed unambiguous assessment of pseudocontact shifts relative to diamagnetic reference states. Because pseudocontact shifts can be observed for protons as much as 20 A from the paramagnetic centre, this approach allows study of electron transfer proteins in fast exchange.

Novel heteronuclear methods of assignment transfer from a diamagnetic to a paramagnetic protein: application to rat cytochrome b5.

15N and 1H resonance assignments for backbone and side-chain resonances of both equilibrium forms of rat ferricytochrome b5 have been obtained, using a combination of novel heteronuclear assignment transfer methods from the known assignments of the diamagnetic protein [Guiles, R. D., Basus, V.

Sequence-specific 1H and 15N resonance assignments for both equilibrium forms of the soluble heme binding domain of rat ferrocytochrome b5.

15N and 1H resonance assignments for backbone and side-chain resonances of both equilibrium forms of rat ferrocytochrome b5 have been obtained, using 15N-1H heteronuclear correlation methods employing globally 15N-labeled protein. Unlike other cytochrome b5 species assigned to date (Guiles et al., 1990) the rat cytochrome exists as an equilibrium distribution of conformers in nearly equal abundance (Lee et al.

Structural studies of cytochrome b5: complete sequence-specific resonance assignments for the trypsin-solubilized microsomal ferrocytochrome b5 obtained from pig and calf.

We report complete sequence-specific proton resonance assignments for the trypsin-solubilized microsomal ferrocytochrome b5 obtained from calf liver. In addition, sequence-specific resonance assignments for the main-chain amino acid protons (i.e.

The S0 state of photosystem II induced by hydroxylamine: differences between the structure of the manganese complex in the S0 and S1 states determined by X-ray absorption spectroscopy.

Hydroxylamine at low concentrations causes a two-flash delay in the first maximum flash yield of oxygen evolved from spinach photosystem II (PSII) subchloroplast membranes that have been excited by a series of saturating flashes of light. Untreated PSII membrane preparations exhibit a multiline EPR signal assigned to a manganese cluster and associated with the S2 state when illuminated at 195 K, or at 273 K in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). We used the extent of suppression of the multiline EPR signal observed in samples illuminated at 195 K to determine the fraction of PSII reaction centers set back to a hydroxylamine-induced S0-like state, which we designate S0*.

The S3 state of photosystem II: differences between the structure of the manganese complex in the S2 and S3 states determined by X-ray absorption spectroscopy.

O2-evolving photosystem II (PSII) membranes from spinach have been cryogenically stabilized in the S3 state of the oxygen-evolving complex. The cryogenic trapping of the S3 state was achieved using a double-turnover illumination of dark-adapted PSII preparations maintained at 240 K. A double turnover of PSII was accomplished using the high-potential acceptor, Q400, which is the high-spin iron of the iron-quinone acceptor complex.

EXAFS structural study of FX, the low-potential Fe-S center in photosystem I.

We present iron extended X-ray absorption fine structure (EXAFS) spectra of a photosystem I core preparation containing FX, the very low potential iron-sulfur cluster in photosystem I. The preparation lacks FA and FB. The amplitude of Fe-Fe backscattering in the EXAFS spectrum indicates that FX may be a [4Fe-4S] cluster and is not a [2Fe-2S] cluster or clusters.

Low-potential iron-sulfur centers in photosystem I: an X-ray absorption spectroscopy study.

We have measured the X-ray absorption spectra of Fe in photosystem I (PS I) preparations from spinach and a thermophilic cyanobacterium, Synechococcus sp., to characterize structures of the Fe complexes that function as electron acceptors in PS I. These acceptors include centers A and B, which are probably typical [4Fe-4S] ferredoxins, and X.

Characterization of the manganese O2-evolving complex and the iron-quinone acceptor complex in photosystem II from a thermophilic cyanobacterium by electron paramagnetic resonance and X-ray absorption spectroscopy.

The Mn donor complex in the S1 and S2 states and the iron-quinone acceptor complex (Fe2+-Q) in O2-evolving photosystem II (PS II) preparations from a thermophilic cyanobacterium, Synechococcus sp., have been studied with X-ray absorption spectroscopy and electron paramagnetic resonance (EPR). Illumination of these preparations at 220-240 K results in formation of a multiline EPR signal very similar to that assigned to a Mn S2 species observed in spinach PS II, together with g = 1.

Comparison of the structure of the manganese complex in the S1 and S2 states of the photosynthetic O2-evolving complex: an x-ray absorption spectroscopy study.

A Mn-containing enzyme complex is involved in the oxidation of H2O to O2 in algae and higher plants. X-ray absorption spectroscopy is well suited for studying the structure and function of Mn in this enzyme complex. Results of X-ray K-edge and extended X-ray absorption fine structure (EXAFS) studies of Mn in the S1 and S2 states of the photosynthetic O2-evolving complex in photosystem II preparations from spinach are presented in this paper.

Structure of the manganese complex of photosystem II upon removal of the 33-kilodalton extrinsic protein: an X-ray absorption spectroscopy study.

The structure of the Mn complex of photosystem II (PSII) was studied by X-ray absorption spectroscopy. Oxygen-evolving spinach PSII membranes containing 4-5 Mn/PSII were treated with 0.8 M CaCl2 to extract the 33-, 24-, and 16-kilodalton (kDa) extrinsic membrane proteins.

Assignment of the g = 4.1 EPR signal to manganese in the S2 state of the photosynthetic oxygen-evolving complex: an X-ray absorption edge spectroscopy study.

X-ray absorption spectroscopy at the Mn K-edge has been utilized to study the origin of the g = 4.1 EPR signal associated with the Mn-containing photosynthetic O2-evolving complex. Formation of the g = 4.