Prevalence of Metabolic Syndrome and Its Risk Factors Influence on Microvascular Complications in Patients With Type 1 and Type 2 Diabetes Mellitus.

BACKGROUND: Diabetes mellitus (DM) long-term macrovascular and microvascular complications pose significant health risks and increase mortality. In DM patients, metabolic syndrome (MetSy) either precedes or coexists with the condition. Central obesity, poor glycemic control, hypertension, elevated triglycerides (TG), and low high-density lipoproteins (HDL-C) are the components of MetSy. The purpose of this study is to investigate related diabetic microvascular complications in type 1 DM (T1DM) by comparing them with type 2 DM (T2DM), determine potential risk factors, and estimate prevalence based on the diagnosis of MetSy. METHODOLOGY: This study included 160 T1DM and 160 T2DM patients, totaling 320 DM patients. It was carried out from April 20, 2022, to September 31, 2023, at the Sheikh Zayed Hospital, Rahim Yar Khan, in the Outdoor Diabetic Clinic and Medicine Department. A unique questionnaire was utilized to gather socio-demographic, general, clinical, and laboratory data for the MetSy criteria set forth by the International Diabetes Federation (IDF). The blood pressure, BMI, and waist circumference (WC) were measured, while venous fasting blood was used to assess biochemical markers such as HDL-C, TG, and fasting blood sugar. The microvascular diabetes complications were identified using abdominal ultrasound, fundus ophthalmoscopy, and routine laboratory tests. We quantified and analyzed these variables individually for T1DM and T2DM patients with or without MetSy and compared them in the presence or absence of diabetes microvascular complications. RESULTS: MetSy prevalence was 25.62% (41, n=160) for T1DM and 60.62% (97, n=160) for T2DM, totaling 43.12%. Among T1DM patients with MetSy, the majority were married males, aged 36-49 years, with a BMI of 26.69±2.20 kg/m2 and a WC of 85.12±4.23, and 67.5% (108) patients had diabetes microvascular complications. Comparatively, in T2DM with MetSy, the majority were married females aged 50-59 years with a BMI of 29.79 ± 4.65 kg/m² and a large WC of 93.43±4.49, and 75% (123) patients had diabetes microvascular complications. Overall, this study noted significant p-values for hypertension, elevated TG, low HDL-c, high WC, obesity, female gender in T2DM, and above 36 years of age in both groups with MetSy. Diabetic retinopathy (DR) at 32.4% (p<0.001) was the most prevalent T1DM microvascular complication, followed by nephropathy (30.6%), neuropathy (DN) at 28.1%, and gastroparesis (DG) at 22.3%. Whereas in T2DM, the prevalence of DN was 36.3% (p<0.001), followed by DKD (29.3%), DG (28.9%), and DR (24.9%). CONCLUSION: Nearly a quarter of T1DM patients had MetSy, with increasing percentages of overweight and obese patients who are more likely to have DR, DKD, or DN. MetSy affects two-thirds of T2DM patients, with married obese females aged 50-59 being more susceptible than males, who are more likely to suffer DN, DKD, or DG. Risk factors that contribute to the MetSy burden in T1DM and T2DM include hypertension, poor glycemic management, low HDL-C, high TG, and a higher BMI or WC. Increasing age, female gender in T2DM, longer diabetes duration, and co-morbid hypertension were independent predictors of microvascular complications. DR, DN, DKD, and gastroparesis are the most prevalent diabetic microvascular sequelae. The clinical management of diabetic patients with healthy lifestyle adaptations, good glycemic control, antihypertensives, and statins will contribute greatly to MetSy prevention.

The immune checkpoint receptor LAG3: Structure, function, and target for cancer immunotherapy.

Lymphocyte activation gene 3 protein (LAG3) is an immune checkpoint receptor that is highly upregulated on exhausted T cells in the tumor microenvironment. LAG3 transmits inhibitory signals to T cells upon binding to MHC class II and other ligands, rendering T cells dysfunctional. Consequently, LAG3 is a major target for cancer immunotherapy with many anti-LAG3 monoclonal antibodies (mAbs) that block LAG3 inhibitory activity in clinical trials. In this review, we examine the molecular basis for LAG3 function in light of recently determined crystal and cryoEM structures of this inhibitory receptor. We review what is known about LAG3 interactions with MHC class II, its canonical ligand, and the newly discovered ligands FGL1 and the T cell receptor (TCR)-CD3 complex, including current controversies over the relative importance of these ligands. We then address the development and mechanisms of action of anti-LAG3 mAbs in clinical trials for cancer immunotherapy. We discuss new strategies to therapeutically target LAG3 using mAbs that not only block the LAG3-MHC class II interaction, but also LAG3 interactions with FGL1 or TCR-CD3, or that disrupt LAG3 dimerization. Finally, we assess the possibility of developing mAbs that enhance, rather than block, LAG3 inhibitory activity as treatments for autoimmune diseases.

Sofosbuvir and Velpatasvir Regimen Outcome for Chronic Hepatitis C Patients With End-Stage Renal Disease Undergoing Hemodialysis.

Background Patients on hemodialysis (HD) are most likely to contract hepatitis C (HCV) infection, which is associated with significant morbidity and disease progression. Direct-acting antivirals (DAAs) are safe and tolerable in chronic kidney disease (CKD) with a 90-100% cure rate, and limited data exist regarding their efficacy in end-stage renal disease (ESRD), particularly for HD patients in South Asia. The study aimed to assess the outcome of a 12-week sofosbuvir (SOF) and velpatasvir (VEL) treatment regimen on ESRD patients with chronic HCV infection undergoing HD in the Pakistani Asian population. Methodology This prospective cohort study was conducted between January 2022 and January 2023 at the outpatient nephrology and gastroenterology clinic of Sheikh Zayed Medical College and Hospital, Rahim Yar Khan, Pakistan. This study included a total of 220 ESRD patients fulfilling the inclusion criteria, aged 20-55 years, who had been undergoing weekly HD sessions for at least two years, with acquired HCV infection. Data on demographic and clinical characteristics were collected through patient interviews. Laboratory and dialysis profiling was executed to assess ESRD and discover the underlying cause by ultrasound abdomen, blood pressure measurement by sphygmomanometer, random blood sugar for diabetes, and taking note of the duration and frequency of dialysis. HCV RNA PCR was done at selected intervals to evaluate the virological response to treatment. Sustained virological response (SVR), liver cirrhosis status, and number of weekly HD sessions were compared at one year of SOF/VEL regimen. Results The mean age of patients with ESRD was 41.8 with a standard deviation (SD) of 9.3 years, and HCV diagnosis was 1.3 years with SD of 0.4 years; 52.7% (n=116) were males, 47.3% (n=104) were females, 75% (n=165) were urban dwellers, and 93.6% (n=206) were married. CKD that requires dialysis was caused mainly by hypertension (78, 35%), diabetes mellitus type 2 (52, 24%), bilateral small kidney disease (40, 18%), and others (34, 16%). One hundred and six (48.2%) received dialysis thrice weekly, 83 (37.7%) twice, and 31 (14.1%) once weekly. The study monitored the rapid virological response (RVR) at four weeks of SOF/VEL regimen in 89.5% of ESRD patients, observed end-of-treatment response (ETR) at 12 weeks in 93.2%, and noted 91.4% SVR response at one year. Only four (1.8%) relapses were observed in the study, which was statistically insignificant. The status of liver cirrhosis showed a 50% improvement, decreasing from 40% to 20%. The frequency of weekly HD sessions decreased from thrice to twice-thrice a week. Conclusion The prevalence of contracting HCV is high among CKD and dialysis ESRD patients. All-oral DAA therapy has revolutionized HCV treatment with co-morbidities. Renal functions improved after the SOF/VEL regimen for chronic HCV infection in ESRD patients undergoing HD, with the number of weekly dialysis sessions reduced and SVR reaching 91.4%. Thus, a single-tablet, pan-genotypic DAA regimen of SOF/VEL for 12 weeks is safe, effective, and tolerable regardless of the underlying etiology of ESRD, complications of cirrhosis, HCV genotype, or previous treatment exposure. The successful treatment of HCV and achieving SVR lowers the risk of ESRD complications, improves extra-hepatic manifestations, and greatly enhances survival. Further studies are warranted after the availability of other DAAs to confirm findings with no limitations.

CryoEM structure of a therapeutic antibody (favezelimab) bound to human LAG3 determined using a bivalent Fab as fiducial marker.

Lymphocyte activation gene 3 protein (LAG3) is an inhibitory receptor that is upregulated on exhausted T cells in tumors. LAG3 is a major target for cancer immunotherapy with many anti-LAG3 antibodies in clinical trials. However, there is no structural information on the epitopes recognized by these antibodies. We determined the single-particle cryoEM structure of a therapeutic antibody (favezelimab) bound to LAG3 to 3.5 Å resolution, revealing that favezelimab targets the LAG3-binding site for MHC class II, its canonical ligand. The small size of the complex between the conventional (monovalent) Fab of favezelimab and LAG3 (∼100 kDa) presented a challenge for cryoEM. Accordingly, we engineered a bivalent version of Fab favezelimab that doubled the size of the Fab-LAG3 complex and conferred a highly identifiable shape to the complex that facilitated particle selection and orientation for image processing. This study establishes bivalent Fabs as new fiducial markers for cryoEM analysis of small proteins.

Metabolic Syndrome in Type 2 Diabetes Mellitus Patients: Prevalence, Risk Factors, and Associated Microvascular Complications.

Background The chronic macro and microvascular complications of diabetes mellitus pose serious health challenges. Metabolic syndrome (MetSy) is characterized by central obesity, glucose intolerance, hyperinsulinemia, low high-density lipoproteins (HDLs), high triglycerides (TGs), and hypertension. MetSy precedes or accompanies diabetes, and it has been linked to an increased risk of cardiovascular disease and premature death. This study aimed to estimate prevalence, identify risk factors, and evaluate associated microvascular complications among MetSy patients with type 2 diabetes mellitus (T2DM). Methodology Over the period of March 20, 2022, to March 31, 2023, a prospective cohort study was conducted at the Outdoor Clinic and Medicine Department of Sheikh Zayed Hospital, Rahim Yar Khan. Based on the International Diabetes Federation MetSy criteria, a total of 160 patients fulfilling the inclusion criteria were selected. A special proforma was used to obtain sociodemographic, clinical, and laboratory variables of MetSy in diabetic participants. Blood pressure and anthropometric measurements such as waist circumference (WC) and body mass index (BMI) were measured. Fasting venous blood was collected to analyze biochemical variables such as fasting blood sugar (FBS), TG, and high-density lipoprotein-cholesterol (HDL-C). The microvascular complications of T2DM were established using fundus ophthalmoscopy and neurological and kidney function assessments with the help of laboratory tests. These variables were matched between MetSy and no MetSy groups along with the presence or absence of diabetes microvascular complications. This information was analyzed based on these assessments and patient interviews. Results Of the 160 T2DM patients, the mean age was 52 years with a predominance of females (51.8%) in the 50-59-year age group (56.8%). The average BMI for females was 29.38 ± 0.54 kg/m², and 32 (20%) had obesity. Females exhibited a large WC of 93.52 ± 1.58 cm, and 48 of 83 females had reported diabetes microvascular complications. A significant p-value was observed for hypertension, high TG, low HDL-C, large WC, obesity, BMI, age, and female gender on comparing diabetics with metabolic syndrome (MetSy+) and those without metabolic syndrome (MetSy-). The prevalence of microvascular complications in T2DM patients with MetSy+ was 52.5% compared with 47.5% in MetSy-. The prevalence of diabetic retinopathy was 24.9% (95% confidence interval (CI) = 20.3%-29.6%), nephropathy was 16.8% (95% CI = 12.8%-20.7%), and neuropathy was 10.8% (95% CI = 7.4%-13.3%). Conclusions The prevalence of MetSy observed among T2DM patients was 65%, with married obese females in the 50-59-year age group being more likely to be affected than males. Hypertension, poor glycemic control, high TG, low HDL-C, and greater anthropometric waist measurements and BMI were additional risk factors that tended to increase the MetSy burden in T2DM. Diabetic retinopathy, nephropathy, and neuropathy were the most prevalent microvascular complications of diabetes, and immediate attention is needed to stop their detrimental effects. Longer uncontrolled diabetes, increasing age, and hypertension were independent predictors of microvascular complications. To further reduce the risks of complications that threaten healthy aging and prognosis for these patients, MetSy screening, health education, and better diabetic management are crucial.

Gastroparesis-Related Symptoms in Patients With Type 2 Diabetes Mellitus: Early Detection, Risk Factors, and Prevalence.

Background The symptoms of gastroparesis, such as bloating, postprandial fullness, early satiety, nausea, and abdominal discomfort, progressively worsen the quality of life of the affected individuals. The diagnosis is established on the assessment of gastric function that confirms delayed gastric emptying in the absence of structural etiologies. This study aimed to detect gastroparesis-related clinical symptoms early in patients with type 2 diabetes mellitus (T2DM), investigate the concomitant risk factors, and evaluate the prevalence. Methodology This study was conducted at the Department of Medicine and Diabetes Outdoor Clinic of Sheikh Zayed Hospital, Rahim Yar Khan from February 13, 2022, to February 11, 2023. The study involved 175 patients with T2DM who reported gastroparesis-related symptoms. The demographic and clinical characteristics, symptom severity, complications, related risk factors, duration of disease, medications, body mass index (BMI), fasting plasma glucose, and glycated hemoglobin (HbA1C) levels were assessed. The severity of diabetic gastroparesis was established using the disease-specific Patient Assessment of Gastrointestinal Disorders-Symptom Severity Index (PAGI-SYM) and the Gastroparesis Cardinal Symptom Index (GCSI). The five-point scale of the PAGI-SYM and the four-degree severity scores of GCSI were assessed. Neuropathy disability scores and motor evacuation functions were analyzed. Data were analyzed from these questionnaires, special proforma, and patient interviews. Results The clinical features of diabetic gastroparesis were observed in 44% of T2DM patients with mild-grade gastroparesis in 38 (21.7%), moderate in 30 (17.1%), and severe-grade gastroparesis-related symptoms in nine (5.2%) patients. The main manifestations were early satiety (45.1%), stomach fullness (44.5%), bloating (38.3%), and nausea (33.1%). Diabetic gastroparesis symptoms were considerably linked to disease duration of more than 10 years (p = 0.02), high HbA1c (p = 0.001), increased fasting blood glucose (p = 0.003), polyneuropathy, cigarette smoking, and history of comorbid conditions (p = 0.009). Obesity and the female gender were the forecasters of the manifestation of at least one cardinal gastroparesis symptom. Conclusions Gastric emptying is significant in the pathogenesis of gastroparesis-related symptoms. Disease duration of more than 10 years, poor glycemic control with hyperglycemia, high HbA1C, polyneuropathy, and cigarette smoking must be considered as predictors for early detection and risk factors for the advancement of gastroparesis in T2DM. Gastroparesis-related common symptoms of early satiety, bloating, and stomach fullness were considerably linked to the additional risk factors of hypercholesteremia, chronic microvascular complications, concomitant cardiovascular diseases, and a positive family history of diabetes mellitus. There was no relationship between BMI, age, types of treatment, and the degree of gastroparesis severity. The prevalence and severity of gastroparesis symptoms were particularly high among obese females with poor glycemic control and longer disease duration.

Magnetic resonance evidence of increased iron content in subcortical brain regions in asymptomatic Alzheimer's disease.

While iron over-accumulation has been reported in late stage Alzheimer's disease (AD), whether this occurs early in the asymptomatic stage of AD remains unknown. We aimed to assess brain iron levels in asymptomatic AD using quantitative MR relaxometry of effective transverse relaxation rate (R2*) and longitudinal relaxation rate (R1), and recruited 118 participants comprised of three groups including healthy young participants, and cognitively normal older individuals without or with positive AD biomarkers based on cerebrospinal fluid (CSF) proteomics analysis. Compared with the healthy young group, increased R2* was found in widespread cortical and subcortical regions in the older groups. Further, significantly higher levels of R2* were found in the cognitively normal older subjects with positive CSF AD biomarker (i.e., asymptomatic AD) compared with those with negative AD biomarker in subcortical regions including the left and right caudate, left and right putamen, and left and right globus pallidus (p < .05 for all regions), suggesting increased iron content in these regions. Subcortical R2* of some regions was found to significantly correlate with CSF AD biomarkers and neuropsychological assessments of visuospatial functions. In conclusion, R2* could be a valuable biomarker for studying early pathophysiological changes in AD.

Predictors Of Re-Bleeding After Oesophageal Variceal Banding In Cirrhotic Patients At 4 Weeks.

BACKGROUND: Acute upper gastrointestinal bleeding is a serious complication in cirrhotic patients. Without recommended management, recurrent bleeding happensin 30-40% within the next 2-3 days, and up to 60% within 1 week. Aim was to determine predictors of re-bleeding after oesophageal variceal banding in cirrhotic patients for 4 weeks. It was a descriptive study, conducted at the Department of Medicine, Sheikh Zayed Hospital, Rahim Yar Khan. Six months from June 21 to December 21, 2021. METHODS: A total of 93patients with active oesophageal variceal bleeding were included in this study. Upper gastrointestinal (UGI) endoscopy was performed to look for bendable varices (grades 1-4) and band ligation was applied. Patients were followed for 4 weeks for the history of hematemesis or Malena, fall in haemoglobin of 2 grams per decilitre or more and endoscopic rebleeding findings. RESULTS: Out of 93 patients, 67(72.0%) were males, while 26(28.0%) were females. The Mean age of the patients was 45.66±16.61 years. According to Child Pugh Classification, the majority of the patients 45(48.4%) had Child-Pugh Class-A, while 33 (35.5%) were Child B and 15 (16.1%) patients belonged to Child-Pugh Class C. Red wale sign was noted in 22 patients (23.7%). Among 93 cirrhotic patients who presented with variceal bleeding, 9 (9.7%) had re-bleeding within 4 weeks. Amongst 9 patients, 8 patients (88.9%) had red wale sign, grade II or above oesophageal varices and belonged to severe liver disease with child class B or C. CONCLUSIONS: Endoscopic variceal band Ligation is an effective treatment modality for the control of oesophageal variceal bleeding. Re-bleeding after band ligation was 9.7%. The major contributing factors to re-bleeding were the severity of cirrhosis, grades and columns of oesophageal varices, number of bands ligation and findings of red wale sign. Increasing age and duration of cirrhosis were contributing predictors of increased re-bleeding risk.

Paraphenylenediamine (Hair Dye) Poisoning: A Prospective Study on the Clinical Outcome and Side Effects Profile.

BACKGROUND: Systemic poisoning with paraphenylenediamine (PPD) also known as Kalapathar, is an emerging suicidal trend in developing south Asian and African countries. The clinical distinction of hair dye toxicity comprises severe angioedema of the face and neck, tongue swelling resulting in upper airway obstruction, acute liver injury, myocarditis, and rhabdomyolysis complicating to acute kidney injury. AIM: To raise awareness, document the characteristic clinical spectra, and prevent and predict the outcome of poisoning (suicidal or accidental) with PPD (hair-dye) based on clinical complications, early baseline laboratory results and creatine phosphokinase (CPK) levels monitoring. PLACE AND DURATION: Department of Medicine and Emergency, Sheikh Zayed Hospital, Rahim Yar Khan. One year of study from August 19, 2021 to August 17, 2022. METHODS: A total of 103 patients, with no comorbidities, who presented with acute PPD poisoning were included in this study. The demographic profile, clinical features, laboratory results, route and mode of intoxication were noted in a special proforma. Furthermore, clinical outcomes in the form of need for tracheostomy or mechanical ventilation, mortality and mean hospital stay were also documented. The percentages were calculated for categorical data like demographic profile, clinical features and clinical outcomes. Mean and standard deviation was calculated for continuous variables, i.e., laboratory parameters. RESULTS: Out of 103 patients, 88 (85.4%) were females who belonged to a low socioeconomic class (89%). The mean age of the patients was 26.39 ± 3.41 years. The majority of cases were suicidal self-poisoning (98%), and the route was oral (98%). In 82 (79.6%) of the patients, the characteristic cervicofacial angioedema, dysphagia, dysphonia, tongue swelling and stridor were noted. Clinical complications such as rhabdomyolysis (67.9%), chocolate-colored urine (82.5%), hepatitis (58.2%), and acute kidney injury (22.3%) were noted in the later clinical stages of PPD poisoning. Emergency tracheostomy was performed in 77.6% of patients. The mortality rate in this study stands at 12.6% and the mean hospital stay at 6.25 ±3.99 days. The mean and standard deviation of serum creatinine, CPK, alanine aminotransferase (ALT), aspartate aminotransferase (AST), total leukocyte count (TLC), and serum potassium were, respectively, noted at 2.431 ± 2.275 mg/dL, 1090.8 ± 218.6 IU/L, 476.8 ± 1038.8 IU/L, 639.1 ± 1006, 11100 ± 4124.1 cells/mm3, and 4.8 ± 1.061 mmol/L. CONCLUSION: PPD is emerging as the poison of choice in suicidal young female patients due to its easy, low-cost availability and higher mortality. The cervicofacial angioedema, tongue swelling and rhabdomyolysis impending acute kidney injury are hallmarks of PPD poisoning. The treatment is largely supportive with no specific antidote available. Early clinical diagnosis and supportive therapeutic management in the form of maintenance of airway patency, timely tracheostomy with post-operative tube care, intravenous medications (fluids, steroids, antihistamine), and renal dialysis can save lives and may lead to full recovery. In addition, strict legal measures should be endorsed to ban the sale and use of lethal PPD in hair dyes.

Frontal Metabolites and Alzheimer's Disease Biomarkers in Healthy Older Women and Women Diagnosed with Mild Cognitive Impairment.

BACKGROUND: Women account for two thirds of the prevalence and incidence of Alzheimer's disease (AD) and mild cognitive impairment (MCI). Evidence suggest that sex may differently influence the expression of proteins amyloid-beta (Aß1-42) and tau, for which early detection is crucial in prevention of the disease. OBJECTIVE: We investigated the effect of aging and cerebrospinal fluid (CSF) levels of Aß1-42 and tau on frontal metabolites measured with proton magnetic resonance spectroscopy (MRS) in a cohort of cognitively normal older women and women with MCI. METHODS: 3T single-voxel MRS was performed on the medial frontal cortex, using Point Resolved Spectroscopy (PRESS) and Mescher-Garwood Point Resolved Spectroscopy (MEGA-PRESS) in 120 women (age range 50-85). CSF samples of Aß1-42 and tau and scores of general cognition were also obtained. RESULTS: Levels of frontal gamma aminobutyric acid (GABA+) were predicted by age, independently of disease and CSF biomarkers. Importantly, levels of GABA+ were reduced in MCI patients. Additionally, we found that levels of N-acetylaspartate relative to myo-inositol (tNAA/mI) predicted cognition in MCI patients only and were not related to CSF biomarkers. CONCLUSION: This study is the first to demonstrate a strong association between frontal GABA+ levels and neurological aging in a sample consisting exclusively of healthy older women with various levels of CSF tau and Aß1-42 and women with MCI. Importantly, our results show no correlation between CSF biomarkers and MRS metabolites in this sample.

Relationships between frontal metabolites and Alzheimer's disease biomarkers in cognitively normal older adults.

Elevated expression of ß-amyloid (Aß1-42) and tau are considered risk-factors for Alzheimer's disease in healthy older adults. We investigated the effect of aging and cerebrospinal fluid levels of Aß1-42 and tau on 1) frontal metabolites measured with proton magnetic resonance spectroscopy (MRS) and 2) cognition in cognitively normal older adults (n = 144; age range 50-85). Levels of frontal gamma aminobutyric acid (GABA+) and myo-inositol relative to creatine (mI/tCr) were predicted by age. Levels of GABA+ predicted cognitive performance better than mI/tCr. Additionally, we found that frontal levels of n-acetylaspartate relative to creatine (tNAA/tCr) were predicted by levels of t-tau. In cognitively normal older adults, levels of frontal GABA+ and mI/tCr are predicted by aging, with levels of GABA+ decreasing with age and the opposite for mI/tCr. These results suggest that age- and biomarker-related changes in brain metabolites are not only located in the posterior cortex as suggested by previous studies and further demonstrate that MRS is a viable tool in the study of aging and biomarkers associated with pathological aging and Alzheimer's disease.

Crystal Structure of a Bivalent Antibody Fab Fragment.

We determined the crystal structure to 1.8 Å resolution of the Fab fragment of an affinity-matured human monoclonal antibody (HC84.26.5D) that recognizes the E2 envelope glycoprotein of hepatitis C virus (HCV). Unlike conventional Fabs, which are monovalent monomers, Fab HC84.26.5D assembles into a bivalent domain-swapped dimer in which the two VL/VH modules are separated by ~25 Å. In solution, Fab HC84.26.5D exists predominantly as a dimer (~80%) in equilibrium with the monomeric form of the Fab (~20%). Dimerization is mediated entirely by deletion of a single residue, VHSer113 (Kabat numbering), in the elbow region linking the VH and CH1 domains. In agreement with the crystal structure, dimeric Fab HC84.26.5D is able to bind two HCV E2 molecules in solution. This is only the second example of a domain-swapped Fab dimer from among >3000 Fab crystal structures determined to date. Moreover, the architecture of the doughnut-shaped Fab HC84.26.5D dimer is completely different from that of the previously reported Fab 2G12 dimer. We demonstrate that the highly identifiable shape of dimeric Fab HC84.26.5D makes it useful as a fiducial marker for single-particle cryoEM analysis of HCV E2. Bivalent domain-swapped Fab dimers engineered on the basis of HC84.26.5D may also serve as a means of doubling the effective size of conventional Fab-protein complexes for cryoEM.

Optimisation of Cu+ impregnation of MOF-74 to improve CO/N2 and CO/CO2 separations.

Carbon monoxide (CO) purification from syngas impurities is a highly energy and cost intensive process. Adsorption separation using metal-organic frameworks (MOFs) is being explored as an alternative technology for CO/nitrogen (N2) and CO/carbon dioxide (CO2) separation. Currently, MOFs' uptake and selectivity levels do not justify displacement of the current commercially available technologies. Herein, we have impregnated a leading MOF candidate for CO purification, i.e. M-MOF-74 (M = Co or Ni), with Cu+ sites. Cu+ allows strong π-complexation from the 3d electrons with CO, potentially enhancing the separation performance. We have optimised the Cu loading procedure and confirmed the presence of the Cu+ sites using X-ray absorption fine structure analysis (XAFS). In situ XAFS and diffuse reflectance infrared Fourier Transform spectroscopy analyses have demonstrated Cu+-CO binding. The dynamic breakthrough measurements showed an improvement in CO/N2 and CO/CO2 separations upon Cu impregnation. This is because Cu sites do not block the MOF metal sites but rather increase the number of sites available for interactions with CO, and decrease the surface area/porosity available for adsorption of the lighter component.

Role of methionine 71 in substrate recognition and structural integrity of bacterial peptidyl-tRNA hydrolase.

BACKGROUND: Bacterial peptidyl-tRNA hydrolase (Pth) is an essential enzyme that alleviates tRNA starvation by recycling prematurely dissociated peptidyl-tRNAs. The specificity of Pth for N-blocked-aminoacyl-tRNA has been proposed to be contingent upon conserved residue N14 forming a hydrogen bond with the carbonyl of the first peptide bond in the substrate. M71 is involved in forming a conserved hydrogen bond with N14. Other interactions facilitating this recognition are not known. METHODS: The structure, dynamics, and stability of the M71A mutant of Pth from Vibrio cholerae (VcPth) were characterized by X-ray crystallography, NMR spectroscopy, MD simulations and DSC. RESULTS: Crystal structure of M71A mutant was determined. In the structure, the dimer interface is formed by the insertion of six C-terminal residues of one molecule into the active site of another molecule. The side-chain amide of N14 was hydrogen bonded to the carbonyl of the last peptide bond formed between residues A196 and E197, and also to A71. The CSP profile of mutation was similar to that observed for the N14D mutant. M71A mutation lowered the thermal stability of the protein. CONCLUSION: Our results indicate that the interactions of M71 with N14 and H24 play an important role in optimal positioning of their side-chains relative to the peptidyl-tRNA substrate. Overall, these interactions of M71 are important for the activity, stability, and compactness of the protein. SIGNIFICANCE: The work presented provides original and new structural and dynamics information that significantly enhances our understanding of the network of interactions that govern this enzyme's activity and selectivity.

Unraveling the stereochemical and dynamic aspects of the catalytic site of bacterial peptidyl-tRNA hydrolase.

Bacterial peptidyl-tRNA hydrolase (Pth; EC 3.1.1.29) hydrolyzes the peptidyl-tRNAs accumulated in the cytoplasm and thereby prevents cell death by alleviating tRNA starvation. X-ray and NMR studies of Vibrio cholerae Pth (VcPth) and mutants of its key residues involved in catalysis show that the activity and selectivity of the protein depends on the stereochemistry and dynamics of residues H24, D97, N118, and N14. D97-H24 interaction is critical for activity because it increases the nucleophilicity of H24. The N118 and N14 have orthogonally competing interactions with H24, both of which reduce the nucleophilicity of H24 and are likely to be offset by positioning of a peptidyl-tRNA substrate. The region proximal to H24 and the lid region exhibit slow motions that may assist in accommodating the substrate. Helix α3 exhibits a slow wobble with intermediate time scale motions of its N-cap residue N118, which may work as a flypaper to position the scissile ester bond of the substrate. Overall, the dynamics of interactions between the side chains of N14, H24, D97, and N118, control the catalysis of substrate by this enzyme.

Structural characterization of peptidyl-tRNA hydrolase from Mycobacterium smegmatis by NMR spectroscopy.

BACKGROUND: Accumulation of toxic peptidyl-tRNAs in the bacterial cytoplasm is averted by the action of peptidyl-tRNA hydrolase (Pth), which cleaves peptidyl-tRNA into free tRNA and peptide. NMR studies are needed for a protein homolog with a complete crystal structure, for comparison with the NMR structure of Mycobacterium tuberculosis Pth. METHODS: The structure and dynamics of Mycobacterium smegmatis Pth (MsPth) were characterized by NMR spectroscopy and MD simulations. The thermal stability of MsPth was characterized by DSC. RESULTS: MsPth NMR structure has a central mixed seven stranded ß-sheet that is enclosed by six α-helices. NMR relaxation and MD simulations studies show that most of the ordered regions are rigid. Of the substrate binding segments, the gate loop is rigid, the base loop displays slow motions, while the lid loop displays fast timescale motions. MsPth displays high thermal stability characterized by a melting temperature of 61.71°C. CONCLUSION: The NMR structure of MsPth shares the canonical Pth fold with the NMR structure of MtPth. The motional characteristics for the lid region, the tip of helix α3, and the gate region, as indicated by MD simulations and NMR data, are similar for MsPth and MtPth. However, MsPth has relatively less rigid base loop and more compactly packed helices α5 and α6. The packing and the dynamic differences appear to be an important contributing factor to the thermal stability of MsPth, which is significantly higher than that of MtPth. SIGNIFICANCE: MsPth structure consolidates our understanding of the structure and dynamics of bacterial Pth proteins.

Expanding access to HIV testing and counseling and exploring vulnerabilities among spouses of HIV-positive men who inject drugs in Pakistan.

OBJECTIVES: To explore the utility of home and community-based HIV testing and counseling (HTC) to increase detection of undiagnosed HIV among female spouses and children of HIV-positive PWID in Punjab province, Pakistan. DESIGN: Between March 2014 and March 2015, home-based HTC was provided by a local NGO to spouses of HIV-positive PWID in Lahore, Faisalabad, and Sargodha. Convenience sampling was used to identify 2400 married, HIV-positive men who inject drugs and who were currently registered and receiving harm reduction services from the NGO 'Roshan Rasta' and seek consent to approach their wives. METHOD: Trained outreach teams conducted HTC and administered a short sociodemographic and behavioral questionnaire to consenting spouses in their homes. HIV-exposed children were also tested with parental consent. RESULTS: of the 2400 married HIV positive male-injecting drug users, only 1959 spouses were approached and 1896 agreed to HTC (96.8%). HIV prevalence was 5.3% (n = 101) among spouses and they had very low level of HIV-related knowledge and protective behaviors CONCLUSION: Home and community-based HTC was effective in identifying undiagnosed HIV among spouses of PWID, the majority of whom reported low rates of prior HIV testing and low HIV-related knowledge. Expansion of HIV prevention services and linkages to treatment and care including PMTCT are urgently needed for this group.

Metal Organic Framework Crystals in Mixed-Matrix Membranes: Impact of the Filler Morphology on the Gas Separation Performance.

Mixed-matrix membranes (MMMs) comprising NH2-MIL-53(Al) and Matrimid® or 6FDA-DAM have been investigated. The MOF loading has been varied between 5 and 20 wt%, while NH2-MIL-53(Al) with three different morphologies: nanoparticles, nanorods and microneedles have been dispersed in Matrimid®. The synthesized membranes have been tested in the separation of CO2 from CH4 in an equimolar mixture. At 3 bar and 298 K for 8 wt% MOF loading, incorporation of NH2-MIL-53(Al) nanoparticles leads to the largest improvement compared to nanorods and microneedles. The incorporation of the best performing filler, i.e. NH2-MIL-53(Al) nanoparticles, to the highly permeable 6FDA-DAM has a larger effect, and the CO2 permeability increased up to 85 % with slightly lower selectivities for 20 wt% MOF loading. Specifically, these membranes have a permeability of 660 Barrer with CO2/CH4 separation factor of 28, leading to a performance very close to the Robeson limit of 2008. Furthermore, a new non-destructive technique based on Raman spectroscopy mapping is introduced to assess the homogeneity of the filler dispersion in the polymer matrix. The MOF contribution can be calculated by modelling the spectra. The determined homogeneity of the MOF filler distribution in the polymer is confirmed by FIB-SEM analysis.

Assessment of electric field distribution in anisotropic cortical and subcortical regions under the influence of tDCS.

The focus of this study is to estimate the contribution of regional anisotropic conductivity on the spatial distribution of an induced electric field across gray matter (GM), white matter (WM), and subcortical regions under transcranial direct current stimulation (tDCS). The assessment was conducted using a passive high-resolution finite element head model with inhomogeneous and variable anisotropic conductivities derived from the diffusion tensor data. Electric field distribution was evaluated across different cortical as well as subcortical regions under four bicephalic electrode configurations. Results indicate that regional tissue heterogeneity and anisotropy cause the pattern of induced fields to vary in orientation and strength when compared to the isotropic scenario. Different electrode montages resulted in distinct distribution patterns with noticeable variations in field strengths. The effect of anisotropy is highly montage dependent and directional conductivity has a more profound effect in defining the strength of the induced field. The inclusion of anisotropy in the GM and subcortical regions has a significant effect on the strength and spatial distribution of the induced electric field. Under the (C3-Fp2) montage, the inclusion of GM and subcortical anisotropy increased the average percentage difference in the electric field strength of brain from 5% to 34% (WM anisotropy only). In terms of patterns distribution, the topographic errors increased from 9.9% to 40% (WM anisotropy only) across the brain.