Vibrational Spectra of a Mechanosensitive Channel

We report the simulated vibrational spectra of a mechanosensitive membrane channel in different gating states. Our results show that while linear absorption is insensitive to structural differences, linear dichroism and sum-frequency generation spectroscopies are sensitive to the orientation of the transmembrane helices, which is changing during the opening process. Linear dichroism cannot distinguish an intermediate structure from the closed structure, but sum-frequency generation can. In addition, we find that two-dimensional infrared spectroscopy can be used to distinguish all three investigated gating states of the mechanosensitive membrane channel.

Neuropsychiatric events at the time of diagnosis of systemic lupus erythematosus - An international inception cohort study

To access publisher full text version of this article. Please click on the hyperlink in Additional Links fieldOBJECTIVE: To describe the prevalence, characteristics, attribution, and clinical significance of neuropsychiatric (NP) events in an international inception cohort of systemic lupus erythematosus (SLE) patients. METHODS: The study was conducted by the Systemic Lupus International Collaborating Clinics (SLICC). Patients were enrolled within 15 months of fulfilling the American College of Rheumatology (ACR) SLE classification criteria. All NP events within a predefined enrollment window were identified using the ACR case definitions of 19 NP syndromes. Decision rules were derived to determine the proportion of NP disease attributable to SLE. Clinical significance was determined using the Short Form 36 (SF-36) Health Survey and the SLICC/ACR Damage Index (SDI). RESULTS: A total of 572 patients (88% female) were recruited, with a mean +/- SD age of 35 +/- 14 years. The mean +/- SD disease duration was 5.2 +/- 4.2 months. Within the enrollment window, 158 of 572 patients (28%) had at least 1 NP event. In total, there were 242 NP events that encompassed 15 of 19 NP syndromes. The proportion of NP events attributed to SLE varied from 19% to 38% using alternate attribution models and occurred in 6.1-11.7% of patients. Those with NP events, regardless of attribution, had lower scores on the SF-36 and higher SDI scores compared with patients with no NP events. CONCLUSION: Twenty-eight percent of SLE patients experienced at least 1 NP event around the time of diagnosis of SLE, of which only a minority were attributed to SLE. Regardless of attribution, the occurrence of NP events was associated with reduced quality of life and increased organ damage

Amide I’-II’ 2D IR spectroscopy provides enhanced protein secondary structural sensitivity

We demonstrate how multimode 2D IR spectroscopy of the protein amide I′ and II′ vibrations can be used to distinguish protein secondary structure. Polarization-dependent amide I′−II′ 2D IR experiments on poly-l-lysine in the β-sheet, α-helix, and random coil conformations show that a combination of amide I′ and II′ diagonal and cross peaks can effectively distinguish between secondary structural content, where amide I′ infrared spectroscopy alone cannot. The enhanced sensitivity arises from frequency and amplitude correlations between amide II′ and amide I′ spectra that reflect the symmetry of secondary structures. 2D IR surfaces are used to parametrize an excitonic model for the amide I′−II′ manifold suitable to predict protein amide I′−II′ spectra. This model reveals that the dominant vibrational interaction contributing to this sensitivity is a combination of negative amide II′−II′ through-bond coupling and amide I′−II′ coupling within the peptide unit. The empirically determined amide II′−II′ couplings do not significantly vary with secondary structure: −8.5 cm−1 for the β sheet, −8.7 cm−1 for the α helix, and −5 cm−1 for the coil.National Science Foundation (U.S.) (CHE-0616575)United States. Dept. of Energy (DE-FG02-99ER14988)United States. Dept. of Defense (National Defense Science and Engineering Graduate Fellowship)Petroleum Research Fun