Accurate measurement of ^{13}C - ^{15}N distances with solid-state NMR

Solid-state NMR technique for measureing distances between hetero-nuclei in static powder samples is described. It is based on a two-dimensional single-echo scheme enhanced with adiabatic cross-polarization. As an example, the results for intra-molecular distances in $\alpha$-crystalline form of glycine are presented. The measured NMR distances ^13 C(2) - ^15 N and ^13 C(1) - ^15 N are 1.496 $\pm$ 0.002 \AA and 2.50 $\pm$ 0.02 \AA, respectively.Comment: 12 page

Assessment of the protein interaction between coagulation factor XII and corn trypsin inhibitor by molecular docking and biochemical validation

Background: Corn trypsin inhibitor (CTI) has selectivity for serine proteases coagulation factor XII (FXII) and trypsin. CTI is in widespread use as a reagent that specifically inhibits the intrinsic pathway of blood coagulation but not the extrinsic pathway. Objectives: To investigate the molecular basis of FXII inhibition by CTI. Methods: We performed molecular docking of CTI, using its known crystal structure, with a model of the activated FXII (FXIIa) protease domain. The interaction model was verified using a panel of recombinant CTI variants tested for their ability to inhibit FXIIa enzymatic activity using a substrate cleavage assay. Results: The docking predicted that (i) the CTI central inhibitory loop P1 Arg34 side chain forms a salt bridge to the FXIIa S1 pocket Asp189 side chain (ii) residue Trp22 from the CTI helix α1 interacts with the FXIIa S3 pocket (iii) Arg43 from CTI helix α2 forms a salt bridge to FXIIa H1 pocket Asp60A. CTI amino acid substitution R34A negated all inhibitory activity whereas variants G32W, L35A, W22A or R42A-R43A reduced activity by a large degree of 108, 41, 158 and 100-fold respectively, with R27A, W37A, W39A, R42A having no effect. Synthetic peptides spanning CTI residues 20-44 had inhibitory activity 3-4000-fold less than full-length CTI. Conclusions: The data confirm the validity of a canonical model of the FXIIa-CTI interaction with helix α1 (Trp22), central inhibitory loop (Arg34) and helix α2 (Arg43) of CTI required for effective binding by contacting the S1, S3 and H1 pockets of FXIIa, respectively

First principles investigations of the electronic, magnetic and chemical bonding properties of CeTSn (T=Rh,Ru)

The electronic structures of CeRhSn and CeRuSn are self-consistently calculated within density functional theory using the local spin density approximation for exchange and correlation. In agreement with experimental findings, the analyses of the electronic structures and of the chemical bonding properties point to the absence of magnetization within the mixed valent Rh based system while a finite magnetic moment is observed for trivalent cerium within the Ru-based stannide, which contains both trivalent and intermediate valent Ce.Comment: 6 pages, 7 figures, for more information see http://www.physik.uni-augsburg.de/~eyert

UV-induced ligand exchange in MHC class I protein crystals

High-throughput structure determination of protein−ligand complexes is central in drug development and structural proteomics. To facilitate such high-throughput structure determination we designed an induced replacement strategy. Crystals of a protein complex bound to a photosensitive ligand are exposed to UV light, inducing the departure of the bound ligand, allowing a new ligand to soak in. We exemplify the approach for a class of protein complexes that is especially recalcitrant to high-throughput strategies: the MHC class I proteins. We developed a UV-sensitive, “conditional”, peptide ligand whose UV-induced cleavage in the crystals leads to the exchange of the low-affinity lytic fragments for full-length peptides introduced in the crystallant solution. This “in crystallo” exchange is monitored by the loss of seleno-methionine anomalous diffraction signal of the conditional peptide compared to the signal of labeled MHC β2m subunit. This method has the potential to facilitate high-throughput crystallography in various protein families

Electronic entropy, shell structure, and size-evolutionary patterns of metal clusters

We show that electronic-entropy effects in the size-evolutionary patterns of relatively small (as small as 20 atoms), simple-metal clusters become prominent already at moderate temperatures. Detailed agreement between our finite-temperature-shell-correction-method calculations and experimental results is obtained for certain temperatures. This agreement includes a size-dependent smearing out of fine-structure features, accompanied by a measurable reduction of the heights of the steps marking major-shell and subshell closings, thus allowing for a quantitative analysis of cluster temperatures.Comment: Latex/Revtex, 4 pages with 3 Postscript figure

Structure of a bacterial cell surface decaheme electron conduit

Some bacterial species are able to utilize extracellular mineral forms of iron and manganese as respiratory electron acceptors. In Shewanella oneidensis this involves decaheme cytochromes that are located on the bacterial cell surface at the termini of trans-outer-membrane electron transfer conduits. The cell surface cytochromes can potentially play multiple roles in mediating electron transfer directly to insoluble electron sinks, catalyzing electron exchange with flavin electron shuttles or participating in extracellular intercytochrome electron exchange along “nanowire” appendages. We present a 3.2-Å crystal structure of one of these decaheme cytochromes, MtrF, that allows the spatial organization of the 10 hemes to be visualized for the first time. The hemes are organized across four domains in a unique crossed conformation, in which a staggered 65-Å octaheme chain transects the length of the protein and is bisected by a planar 45-Å tetraheme chain that connects two extended Greek key split ß-barrel domains. The structure provides molecular insight into how reduction of insoluble substrate (e.g., minerals), soluble substrates (e.g., flavins), and cytochrome redox partners might be possible in tandem at different termini of a trifurcated electron transport chain on the cell surface

Effects of SlowMo, a Blended Digital Therapy Targeting Reasoning, on Paranoia Among People With Psychosis: A Randomized Clinical Trial.

IMPORTANCE: Persistent paranoia is common among patients with psychosis. Cognitive-behavioral therapy for psychosis can be effective. However, challenges in engagement and effectiveness remain. OBJECTIVE: To investigate the effects on paranoia and mechanisms of action of SlowMo, a digitally supported reasoning intervention, plus usual care compared with usual care only. DESIGN, SETTING, AND PARTICIPANTS: This parallel-arm, assessor-blinded, randomized clinical trial recruited participants at UK community health services from May 1, 2017, to May 14, 2019. Eligible participants consisted of a referral sample with schizophrenia-spectrum psychosis and distressing, persistent (≥3 months) paranoia. INTERVENTIONS: Individuals were randomized 1:1 to SlowMo, consisting of 8 digitally supported face-to-face sessions and a mobile app, plus usual care (n = 181) and usual care only (n = 181). MAIN OUTCOMES AND MEASURES: The primary outcome was paranoia, measured by the Green et al Paranoid Thoughts Scale (GPTS) total score at 24 weeks. Secondary outcomes included GPTS total score at 12 weeks and GPTS Part A (reference) and Part B (persecutory) scores, the Psychotic Symptom Rating Scales (PSYRATS Delusion subscale), reasoning (belief flexibility, possibility of being mistaken [Maudsley Assessment of Delusions, rated 0%-100%]), and jumping to conclusions (Beads Task). RESULTS: A total of 361 participants were included in intention-to-treat analysis, of whom 252 (69.8%) were male and 249 (69.0%) were White; the mean (SD) age was 42.6 (11.6) years. At 24 weeks, 332 participants (92.0%) provided primary outcome data. Of 181 participants in the SlowMo group, 145 (80.1%) completed therapy. SlowMo plus usual care was not associated with greater reductions than usual care in GPTS total score at 24 weeks (Cohen d, 0.20; 95% CI, −0.02 to 0.40; P = .06). There were significant effects on secondary paranoia outcomes at 12 weeks, including GPTS total score (Cohen d, 0.30; 95% CI, 0.09-0.51; P = .005), Part A score (Cohen d, 0.22; 95% CI, 0.06-0.39; P = .009), and Part B score (Cohen d, 0.32; 95% CI, 0.08-0.56; P = .009), and at 24 weeks, including Part B score (Cohen d, 0.25; 95% CI, 0.01-0.49; P = .04) but not Part A score (Cohen d, 0.12; 95% CI, −0.05 to 0.28; P = .18). Improvements were observed in an observer-rated measure of persecutory delusions (PSYRATS delusion) at 12 weeks (Cohen d, 0.47; 95% CI, 0.17-0.78; P = .002) and 24 weeks (Cohen d, 0.50; 95% CI, 0.20-0.80; P = .001) and belief flexibility at 12 weeks (Cohen d, 0.29; 95% CI, 0.09-0.49; P = .004) and 24 weeks (Cohen d, 0.28; 95% CI, 0.08-0.49; P = .005). There were no significant effects on jumping to conclusions. Improved belief flexibility and worry mediated paranoia change (range mediated, 36%-56%). CONCLUSIONS AND RELEVANCE: SlowMo did not demonstrate significant improvements in the primary measure of paranoia at 24 weeks; however, a beneficial effect of SlowMo on paranoia was indicated by the results on the primary measure at an earlier point and on observer-rated paranoia and self-reported persecution at 12 and 24 weeks. Further work to optimize SlowMo’s effects is warranted. TRIAL REGISTRATION: isrctn.org Identifier: ISRCTN 3244867