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Femtosecond spectroscopy of the first events of the photochemical cycle in bacteriorhodopsin

The first steps in the photochemistry of bacteriorhodopsin (BR) are investigated with light pulses of 160 fs duration. Four samples are studied: (i) the purple membrane, (ii) deuterated purple membrane, (iii) BR trimers and (iv) BR monomers. In all samples the first intermediate J is formed within 430±50 fs. No isotope effect is observed in the formation of J upon deuteration, in contrast to previous reports with much higher excitation energies. Thus proton movement to or from the retinal Schiff's base is not relevant during the first step. Comparing the data for trimeric and monomeric BR suggests an upper limit of 50 fs for the transfer of excitation energy from the excitonically coupled trimer to a single retinal chromophore

Early picosecond events in the photo cycle of Bacteriorhodopsin

The primary processes of the photochemical cycle of light-adapted bacteriorhodopsin (BR) were studied by various experimental techniques with a time resolution of 5 × 10-13 s. The following results were obtained. (a) After optical excitation the first excited singlet state S1 of bacteriorhodopsin is observed via its fluorescence and absorption properties. The population of the excited singlet state decays with a lifetime τ1 of ~0.7 ps (430 ± 50 fs) (52). (b) With the same time constant the first ground-state intermediate J builds up. Its absorption spectrum is red-shifted relative to the spectrum of BR by ~30 nm. (c) The second photoproduct K, which appears with a time constant of τ2 = 5 ps shows a red-shift of 20 nm, relative to the peak of BR. Its absorption remains constant for the observation time of 300 ps. (d) Upon suspending bacteriorhodopsin in D2O and deuterating the retinal Schiff base at its nitrogen (lysine 216), the same photoproducts J and K are observed. The relaxation time constants τ1 and τ2 remain unchanged upon deuteration within the experimental accuracy of 20%

Patient and Physician Determinants of Implantable Cardioverter Defibrillator Use in the Heart Failure Population

Recent studies report surprisingly low rates of implantable cardioverter defibrillator (ICD) placement for primary prevention against sudden cardiac death among patients with heart failure and left ventricular systolic dysfunction. Reasons for the low rates of utilization are not well understood. The authors examined ICD implantation rates at a university-based tertiary care center and used multivariable analysis to identify independent factors associated with ICD utilization. The ICD implantation rate for 850 eligible patients was 70%. Forty-seven (18%) patients refused implantation; women were twice as likely to refuse compared to men (8% vs 4%, P=.013). Race was not associated with utilization. On multivariable analysis, independent predictors of implantation included having a heart failure specialist (odds ratio [OR], 8.13; P<.001) or general cardiologist (OR, 2.23; P=.13) managing care, age range 70 to 79 (OR, 0.55; P<.001) or 80 and older (OR, 0.26; P<.001), female sex (OR, 0.49; P<.001), QRS interval (OR, 1.016; P<.001), diastolic blood pressure (OR, 0.979; P=.011), cerebrovascular disease (OR, 0.44; P=.007), and dementia (OR, 0.13; P=.002). Our registry of patients with cardiomyopathy and heart failure reveals that high rates of utilization are possible. Factors closely associated with ICD utilization include type of physician coordinating care, age, and comorbidities. Congest Heart Fail. 2010;16:141–146. © 2010 Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78684/1/j.1751-7133.2009.00139.x.pd

Optical picosecond studies of bacteriorhodopsin containing a sterically fixed retinal

The photochemical behaviour of an analogous bacteriorhodopsin (9,12-Ph-BR) which contains the sterically fixed 9,12-phenylretinal has been investigated with picosecond spectroscopy. The following results have been obtained. No ground-state intermediate photoproduct is found in agreement with the previous observation that 9,12-Ph-BR does not exhibit proton pumping under illumination. The excited singlet state has a lifetime of τS = 10 ± 2 ps. This lifetime agrees favourably with the value calculated from the radiative lifetime τrad = 6.2 ns and the fluorescence quantum efficiency of 1.2·10−3. Excited-state absorption occurs which results in fluorescence in the ultraviolet region. These various observations differ drastically from the corresponding findings on bacteriorhodopsin. Most important for an understanding of the differences is the fact that 9,12-phenylretinal does not isomerize in the protein's binding site in contrast to retinal. Our data therefore suggest that the formation of the intermediate K observed in bacteriorhodopsin is accompanied by the all-trans to 13-cis isomerization

UAl2:Fine structure of the f bands

The electronic structure of the C15, or cubic-Laves-phase material, UAl2 has been calculated using the linearized relativistic augmented-plane-wave method. The anomalous behavior of the electrical resistivity, specific heat, and magnetic susceptibility can be explained by the fine structure of the density of states near the Fermi energy alone, without the necessity of the introduction of drastic spin fluctuations or many-body effects

Femtosecond spectroscopy of the first events of the photochemical cycle in bacteriorhodopsin

The first steps in the photochemistry of bacteriorhodopsin (BR) are investigated with light pulses of 160 fs duration. Four samples are studied: (i) the purple membrane, (ii) deuterated purple membrane, (iii) BR trimers and (iv) BR monomers. In all samples the first intermediate J is formed within 430±50 fs. No isotope effect is observed in the formation of J upon deuteration, in contrast to previous reports with much higher excitation energies. Thus proton movement to or from the retinal Schiff's base is not relevant during the first step. Comparing the data for trimeric and monomeric BR suggests an upper limit of 50 fs for the transfer of excitation energy from the excitonically coupled trimer to a single retinal chromophore

A Web Application for Self-Monitoring Improves Symptoms in Chronic Systolic Heart Failure

Objective: The objective of this study was to determine if a Web application that promoted mindfulness of the progress of the chronic disease through self-monitoring improved quality of life in heart failure. Materials and Methods: This was a prospective single-center single-group study. Participants were instructed how to use the Web application and to perform self-monitoring daily for 12 weeks. A comprehensive physical exam, assessment of New York Heart Association (NYHA) class, the Minnesota Living with Heart Failure Questionnaire (MLHFQ), and an evaluation of self-management were performed in person at baseline and at 12 weeks. Results: Participants consisted of older (mean, 59 years), predominantly female (63%) adults with NYHA class II or III symptoms. NYHA classification (preintervention versus postintervention, 2.5±0.13 versus 2.0±0.13; p=0.0032) and MLHFQ score (55.7±4.6 versus 42.6±5.1, respectively; p=0.0078) improved over 12 weeks of self-monitoring. A trend toward improvement was also demonstrated in weight (preintervention versus postintervention, 209±9.6 pounds versus 207±9.4 pounds; by paired t test, p=0.389), number of times exercised per week (1.29±0.5 versus 2.5±0.6, respectively; p=0.3), and walk distance (572±147 yards versus 845±187 yards, respectively; p=0.119). Jugular venous distention (preintervention versus postintervention, 8.1±0.6?cm versus 6.7±0.3?cm; p=0.083) and peripheral edema (29.2% versus 16.7%, respectively; p=0.375) decreased after 12 weeks of self-monitoring via the Web application. Conclusions: A Web application for self-monitoring heart failure over 12 weeks improved both NYHA classification and MLHFQ score. The trend in improved physical activity and physical exam support these outcomes. The number of patients reporting a sodium-restricted diet increased over the 12 weeks, which may have led to the positive findings.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140281/1/tmj.2014.0095.pd