QM/MM Investigation for Protonation States in a Bilin Reductase PcyA-Biliverdin IXα Complex.

Herein we report quantum mechanical/molecular mechanical (QM/MM) studies to investigate the most probable protonation states of active site amino acids and bound substrate based on a recently reported neutron diffraction structure of phycocyanobilin:ferredoxin oxidoreductase (PcyA) by Unno et al. This structure was considered to be bound in its initial state of biliverdin IXα (BV), which has the C-pyrrole ring in the deprotonated state. The protonation state of BV suggested by neutron and spectroscopic studies is a stable, two-electron reduced complex with a bound hydronium ion. Several ambiguities in the neutron structure were observed which prompted a further theoretical analysis of the structure. This structural investigation provides new understanding of the PcyA and BV protonation states not previously reported in the literature. Our calculations suggest that the hydronium ion (H3 O+ ) is energetically unfavorable, preferentially protonating the neighboring His88 residue and that the C-ring of BV is not protonated.

Multiple deletions in mitochondrial DNA in a patient with progressive external ophthalmoplegia, leukoencephalopathy and hypogonadism.

Progressive external ophthalmoplegia (PEO) is one of a number of major types of mitochondrial disorders. Most sporadic PEO patients have a heteroplasmic large deletion of mitochondrial DNA (mtDNA) in the mitochondria in skeletal muscles. We herein analyzed mtDNA deletions using sub-cloning and Sanger sequencing of PCR products in a 31-year-old Japanese man with multiple symptoms, including PEO, muscle weakness, hearing loss, leukoencephalopathy and hypogonadism. A large number of multiple deletions was detected, as well as four kinds of deletion breakpoints identified in different locations, including m.3347_12322, m.5818_13964, m.5829_13964 and m.5837_13503.

Predictors for hemorrhagic transformation with intravenous tissue plasminogen activator in acute ischemic stroke.

We examined the predictive value of clinical and radiological findings, including cerebral microbleeds (CMBs) seen in gradient-echo T2*-weighted magnetic resonance images, for hemorrhagic transformation (HT) following ischemic stroke, in ischemic stroke patients treated with recombinant tissue plasminogen activator (rt-PA). The subjects were 71 patients with acute ischemic stroke treated with rt-PA (50 males, 21 females; mean age±standard deviation 73±10 years; 53 cardiogenic stroke, 18 atherothrombotic). HT on computed tomography (CT)(mean: 24 hours after onset) was seen in 26 (37%) subjects. The mean Alberta stroke programme early CT score on diffusion-weighted images (ASPECTS-DWI) score was significantly lower in the group with HT than that in the group without HT (6.5±2.3 vs 8.4±1.6, P<0.001). Prevalence of CMBs was not significantly different between the groups with and without HT. Relative risk of various factors for appearance of HT was evaluated by logistic regression analysis. Increased ASPECTS-DWI score showed a significantly reduced relative risk for HT (odds ratio: 0.54, 95% confidence interval: 0.33-0.87), while the influence of CMBs (1.22, 0.23-6.53) was not significant. In conclusion, ASPECTS-DWI score (a measure of the volume of ischemic tissue) is a useful marker for predicting HT. On the other hand, CMBs on T2*-weighted images may not be predictive for HT in patients treated with intravenous rt-PA.