Long-distance perturbation on Schiff base-counterion interactions by His30 and the extracellular Na-binding site in Krokinobacter rhodopsin 2.

Krokinobacter rhodopsin 2 (KR2), a light-driven Na+ pump, is a dual-functional protein, pumping protons in the absence of Na+ when K+ or larger alkali metal ions are present. A specific mutation in helix A near the extracellular Na+ binding site, H30A, eliminates its proton pumping ability. We induced structural changes in H30A by altering the alkali metal ion bound at the extracellular binding site, and observed a strong electrostatic interaction between the Schiff base and counterion and torsion around the Schiff base as revealed by solid-state nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopies.

Stoichiometry and phosphoisotypes of hippocampal AMPA-type glutamate receptor phosphorylation.

It has been proposed that the AMPAR phosphorylation regulates trafficking and channel activity, thereby playing an important role in synaptic plasticity. However, the actual stoichiometry of phosphorylation, information critical to understand the role of phosphorylation, is not known because of the lack of appropriate techniques for measurement. Here, using Phos-tag SDS-PAGE, we estimated the proportion of phosphorylated AMPAR subunit GluA1.

A possible role of chenodeoxycholic acid and glycine-conjugated bile acids in fibrotic steatohepatitis in a dietary rat model.

Background And Aims: Our previous study indicated that hepatic bile acids (BAs) may have deposited and stimulated the pathogenesis of a high fat-cholesterol (HFC) diet-induced fibrotic steatohepatitis in stroke-prone spontaneously hypertensive 5/Dmcr rats, based on dysregulated BA homeostasis pathways. We aimed to further characterize BA profiles in liver and evaluate their relationships to liver injury using this model.

Methods: Hepatic 21 BA levels were determined by ultra-performance liquid chromatography-tandem mass spectrometry, and their correlations with macrovesicular steatosis score, serum alanine aminotransferase (ALT) level and quantified fibrotic area were assessed using Spearman and Pearson correlations.

Simple and rapid quantitation of 21 bile acids in rat serum and liver by UPLC-MS-MS: effect of high fat diet on glycine conjugates of rat bile acids.

In this report, we present a simple and rapid method for analysis of 21 kinds of bile acids and the conjugates in rat serum and liver samples by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS-MS) in the negative ionization mode, using cholic-2, 2, 4, 4-d4 acid as internal standard. After liquid-liguid extraction from serum and liver samples, specimens were analyzed by UPLC equipped with an Acquity TQD tandem quadrupole mass spectrometer. All of the 21 bile acids were sufficiently separated within 5 min.

Diagnosis of fulminant type 1 diabetes mellitus in an autopsy case with postmortem changes.

A Japanese female in her thirties was found dead in her apartment; the postmortem interval was estimated to be approximately 3 days. Several postmortem changes were evident. Acute gastroenteritis had been diagnosed 3 days earlier.

High-throughput and simultaneous analysis of eight central-acting muscle relaxants in human plasma by ultra-performance liquid chromatography-tandem mass spectrometry in the positive and negative ionization modes.

In this report, a high-throughput and sensitive method for analysis of eight central-acting muscle relaxants in human plasma by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) in the positive and negative ionization modes using tolbutamide as internal standard is presented. After pretreatment of a plasma sample by solid-phase extraction with an Oasis HLB cartridge, muscle relaxants were analyzed by UPLC with Acquity UPLC BEH C(18) column and Acquity TQD tandem quadrupole mass spectrometer equipped with an electrospray ionization interface. The calibration curves for muscle relaxants spiked into human plasma equally showed good linearities in the nanogram per milliliter order range.

Sensitive analysis of blonanserin, a novel antipsychotic agent, in human plasma by ultra-performance liquid chromatography-tandem mass spectrometry.

A rapid and sensitive method for analysis of blonanserin in human plasma by ultra-performance liquid chromatography-tandem mass spectrometry is presented. After pretreatment of a plasma sample by solid-phase extraction, blonanserin was analyzed by the system with a C(18) column. This method gave satisfactory recovery rates, reproducibility, and good linearity of calibration curve in the range of 0.

Decomposition of protein nitrosothiolsin matrix-assisted laser desorption/ionization and electrospray ionization mass spectrometry.

The S-nitrosylation of proteins is involved in the trafficking of nitric oxide (NO) in intra- and extracellular milieus. To establish a mass spectrometric method for identifying this post-translational modification of proteins, a synthetic peptide and transthyretin were S-nitrosylated in vitro and analyzed by electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The intact molecular ion species of nitrosylated compounds was identified in the ESI mass spectrum without elimination of the NO group.