Pick-up and assembling of chemically sensitive van der Waals heterostructures using dry cryogenic exfoliation.

Assembling atomic layers of van der Waals materials (vdW) combines the physics of two materials, offering opportunities for novel functional devices. Realization of this has been possible because of advancements in nanofabrication processes which often involve chemical processing of the materials under study; this can be detrimental to device performance. To address this issue, we have developed a modified micro-manipulator setup for cryogenic exfoliation, pick up, and transfer of vdW materials to assemble heterostructures. We use the glass transition of a polymer PDMS to cleave a flake into two, followed by its pick-up and drop to form pristine twisted junctions. To demonstrate the potential of the technique, we fabricated twisted heterostructure of Bi2Sr2CaCu2O8+x (BSCCO), a van der Waals high-temperature cuprate superconductor. We also employed this method to re-exfoliate NbSe2 and make twisted heterostructure. Transport measurements of the fabricated devices indicate the high quality of the artificial twisted interface. In addition, we extend this cryogenic exfoliation method for other vdW materials, offering an effective way of assembling heterostructures and twisted junctions with pristine interfaces.

High-temperature Josephson diode.

Many superconducting systems with broken time-reversal and inversion symmetry show a superconducting diode effect, a non-reciprocal phenomenon analogous to semiconducting p-n-junction diodes. While the superconducting diode effect lays the foundation for realizing ultralow dissipative circuits, Josephson-phenomena-based diode effect (JDE) can enable the realization of protected qubits. The superconducting diode effect and JDE reported thus far are at low temperatures (~4 K), limiting their applications. Here we demonstrate JDE persisting up to 77 K using an artificial Josephson junction of twisted layers of Bi2Sr2CaCu2O8+δ. JDE manifests as an asymmetry in the magnitude and distributions of switching currents, attaining the maximum at 45° twist. The asymmetry is induced by and tunable with a very small magnetic field applied perpendicular to the junction and arises due to interaction between Josephson and Abrikosov vortices. We report a large asymmetry of 60% at 20 K. Our results provide a path towards realizing superconducting Josephson circuits at liquid-nitrogen temperature.

A Functionalizable Analog of the Yariv Reagent for AGP Imaging using Fluorescence Microscopy.

Small molecule fluorescent probes that bind selectively to plant cell wall polysaccharides have been instrumental in elucidating the localization and function of these glycans. Arabinogalactan proteins (AGPs) are cell wall proteoglycans implicated in essential functions such as cell signaling, plant growth, and programmed cell death. There is currently no small molecule probe capable of fluorescently labeling AGPs. The Yariv reagents are the only small molecules that bind AGPs, and have been used to study AGP function and isolate AGPs via precipitation of an AGP-Yariv complex. However, the Yariv reagents are not fluorescent, rendering them ineffective for localization studies using fluorescence microscopy. A fluorescent version of a Yariv reagent that is capable of both binding as well as imaging AGPs would provide a powerful tool for studying AGPs in planta. Herein, we describe the synthesis of an azido analog of the Yariv reagent that can be further functionalized with a fluorophore to provide a glycoconjugate that binds AGPs and is fluorescent. We show that the modified reagent binds gum arabic in in vitro binding assays when used in conjunction with the ßGlcYariv reagent. Fluorescent imaging of AGPs in fixed maize leaf tissue enables localization of AGPs to cell walls in the leaf. Significantly, imaging can also be carried out using fresh tissue. This represents the first small molecule probe that can be used to visualize AGPs using fluorescence microscopy.

Business meetings in a postpandemic world: When and how to meet virtually.

The COVID-19 pandemic that erupted in 2020 forced businesses across the world to adopt virtual meetings. With many people working from home, software platforms like Zoom and Teams became ubiquitous, but their widespread use also revealed many weaknesses and limitations. While technologies for virtual meetings have existed for decades, these technologies have advanced significantly in recent years, and today range from audioconference facilities to telepresence rooms with high-resolution video and sophisticated virtual presence features. The available alternatives differ significantly in costs, complexity and capabilities, and choosing the most effective technology for each meeting setting is not always easy. This is important, since after the pandemic, virtual meetings will move from being a necessity brought on by the pandemic to being a widely accepted alternative to traditional face-to-face meetings. Consequently, the questions of when and how to meet virtually will become even more significant. In this article, we describe a decision-making framework for choosing when and how to meet virtually, based on matching the appropriate communication capabilities with various meeting objectives and taking into account meeting size and duration. The framework is based on extensive empirical research conducted in partnership with several major U.S. and European companies.

Inhibition of Streptococcus pneumoniae growth by masarimycin.

Despite renewed interest, development of chemical biology methods to study peptidoglycan metabolism has lagged in comparison to the glycobiology field in general. To address this, a panel of diamides were screened against the Gram-positive bacterium Streptococcus pneumoniae to identify inhibitors of bacterial growth. The screen identified the diamide masarimycin as a bacteriostatic inhibitor of S. pneumoniae growth with an MIC of 8 µM. The diamide inhibited detergent-induced autolysis in a concentration-dependent manner, indicating perturbation of peptidoglycan degradation as the mode-of-action. Cell based screening of masarimycin against a panel of autolysin mutants, identified a higher MIC against a ΔlytB strain lacking an endo-N-acetylglucosaminidase involved in cell division. Subsequent biochemical and phenotypic analyses suggested that the higher MIC was due to an indirect interaction with LytB. Further analysis of changes to the cell surface in masarimycin treated cells identified the overexpression of several moonlighting proteins, including elongation factor Tu which is implicated in regulating cell shape. Checkerboard assays using masarimycin in concert with additional antibiotics identified an antagonistic relationship with the cell wall targeting antibiotic fosfomycin, which further supports a cell wall mode-of-action.

The Chirality of Aggregated Yariv Reagents Correlates with Their AGP-Binding Ability.

Yariv reagents are glycosylated triphenylazo dyes that bind to arabinogalactan proteins (AGPs), proteoglycans found in plant cell walls that are integral for plant growth and development. Yariv reagents are widely utilized as imaging, purification, and quantification tools for AGPs and represent the only small molecule probe for interrogating AGP function. The ability of Yariv reagents to bind to AGPs is dependent on the structure of the terminal glycoside on the dye. The reason for this selectivity has not been understood until the present work. Using circular dichroism spectroscopy, we show that the Yariv reagents form supramolecular aggregates with helical chirality. More significantly, the ability of the Yariv reagent to bind AGPs is correlated with this helical chirality. This finding paves the way towards developing a more detailed understanding of the nature of the Yariv-AGP complex, and the design of AGP-binding reagents with higher affinities and selectivities.

Detection of ligand binding to glycopolymers using saturation transfer difference NMR.

We report the use of saturation transfer difference (STD) NMR spectroscopy to observe the interaction of various phenylboronic acids (PBAs) with synthetic glycopolymers presenting galactose and glucose. After optimizing experimental parameters to maximize spin diffusion within the glycopolymers, STD NMR experiments were successfully used to detect binding of PBAs to the polymers. Amplification factor build-up curves in conjunction with differential epitope mapping experiments were used to generate an epitope map for the bound boronic acids. STD NMR was also used to detect the interaction between indole and a galactosylated glycopolymer, providing an indole-based view of this CH-π interaction, a common binding motif in carbohydrate recognition.

An Improved Protocol for the Synthesis and Purification of Yariv Reagents.

Yariv reagents are glycoconjugate tris-azo dyes widely used in plant biology. These reagents are synthesized by diazo coupling between phloroglucinol and a para-diazophenyl glycoside. Despite their synthetic accessibility, well-defined protocols for obtaining pure Yariv reagents, and their complete compound characterization data, have not been reported. We report here optimized protocols used to synthesize, purify, and characterize a panel of six Yariv reagents and suggest approaches that could be valuable for the purification and characterization of other glycoconjugates as well.

Outcomes of Deceased Donor Kidney Transplantation Using Expanded Criteria Donor Kidneys Following Pulsatile Preservation.

Aim We compared the outcomes of transplanting expanded criteria donor (ECD) kidneys undergoing machine perfusion (MP) versus cold storage (CS). Material and methods Data on all expanded criteria deceased donor kidney transplants performed at the University of Pittsburgh Medical Center from January 2003 through December 2012 were collected from an in-house electronic repository. There were 78 patients in the MP group and 101 patients in the CS group. The majority of the ECD kidneys were imported from other organ procurement organizations: 69 of 73 in the MP group (94.5%, 5 from unknown sources); and 90 of 99 in the CS group (91%), 2 from an unknown source). Most of the patients in the MP group (77 of 78) received a combination of MP and static CS. MP was performed just prior to transplantation in all MP patients. We used descriptive statistics to characterize our sample. We used logistic regression analysis to model the binary outcome of delayed graft function (DGF; i.e., "yes/no") and Cox (proportional hazard) regression to model time until graft failure. The Kaplan-Meier product-limit method was used to estimate survival curves for graft and patient survival. Results A total of 179 transplants were done from ECD donors (MP, 78; CS, 101). The mean static cold storage time was 14 ± 4.1 hours and the mean machine perfusion time was 11.2 ± 6.3 hours in the MP group. The donor creatinine was higher (1.3 ± 0.6 mg/dl vs. 1.2 ± 0.4 mg/dl, p = 0.01) and the cold ischemia time was longer (28.9 ± 10 hours vs. 24 ± 7.9 hours, p = 0.0003) in the MP patients. There were no differences between the two groups in DGF rate (20.8% [MP] vs. 25.8% [CS], p = 0.46), six-year patient survival (74% [MP] vs. 63.2% [CS], p = 0.11), graft survival (64.3% [MP] vs. 51.5% [CS], p = 0.22), and serum creatinine levels (1.5 mg/dl vs. 1.5 mg/dl) on univariate analysis. On unadjusted analysis, MP subjects without DGF had longer graft survival compared to CS subjects with DGF (p < 0.0032) and MP subjects with DGF (p < 0.0005). MP subjects without DGF had longer death-censored graft survival compared to CS subjects with DGF (p < 0.0077) and MP subjects with DGF (p < 0.0016). However, on regression analysis, MP subjects had longer graft survival than CS subjects when DGF was not present. MP subjects without DGF had longer patient survival compared to CS subjects with DGF (p < 0.0289), on unadjusted analysis. MP subjects had a reduced risk of graft failure (hazard ratio [HR], 0.34; 95% confidence interval [CI], 0.17, 0.68) and death-censored graft failure (HR, 0.44; 95% CI, 0.19, 1.00), compared to CS subjects when DGF was not present. Conclusions Reduction of DGF rates for imported ECD kidneys is vital to optimize outcomes and increase their utilization. One strategy to decrease DGF rates may be to reduce static CS time during transportation, by utilizing a portable kidney perfusion machine.

Diamide Inhibitors of the Bacillus subtilis N-Acetylglucosaminidase LytG That Exhibit Antibacterial Activity.

N-Acetylglucosaminidases (GlcNAcases) play an important role in the remodeling and recycling of bacterial peptidoglycan by degrading the polysaccharide backbone. Genetic deletions of autolysins can impair cell division and growth, suggesting an opportunity for using small molecule autolysin inhibitors both as tools for studying the chemical biology of autolysins and also as antibacterial agents. We report here the synthesis and evaluation of a panel of diamides that inhibit the growth of Bacillus subtilis. Two compounds, fgkc (21) and fgka (5), were found to be potent inhibitors (MIC 3.8 ± 1.0 and 21.3 ± 0.1 µM, respectively). These compounds inhibit the B. subtilis family 73 glycosyl hydrolase LytG, an exo GlcNAcase. Phenotypic analysis of fgkc (21)-treated cells demonstrates a propensity for cells to form linked chains, suggesting impaired cell growth and division.

Plausible Role of Acute HIV Infection Mediated Immune Activation in Causing Renal Allograft Rejection: A Case Report.

Current research states that AIDS pathogenesis has its roots in a chronic activation of immune system secondary to human immunodeficiency virus (HIV)-induced proliferation of T cells, B cells, NK cells, and macrophages. Immune activation due to acute HIV infection can be highly detrimental to allograft survival in a renal transplant recipient. In this report, we describe a 32-year-old African-American male patient who underwent a second live donor renal transplant, following which he developed acute allograft rejection coincident with newly acquired HIV seropositivity.

Recipient Criteria Predictive of Graft Failure in Kidney Transplantation.

Several classifications systems have been developed to predict outcomes of kidney transplantation based on donor variables. This study aims to identify kidney transplant recipient variables that would predict graft outcome irrespective of donor characteristics. All U.S. kidney transplant recipients between October 25,1999 and January 1, 2007 were reviewed. Cox proportional hazards regression was used to model time until graft failure. Death-censored and nondeath-censored graft survival models were generated for recipients of live and deceased donor organs. Recipient age, gender, body mass index (BMI), presence of cardiac risk factors, peripheral vascular disease, pulmonary disease, diabetes, cerebrovascular disease, history of malignancy, hepatitis B core antibody, hepatitis C infection, dialysis status, panel-reactive antibodies (PRA), geographic region, educational level, and prior kidney transplant were evaluated in all kidney transplant recipients. Among the 88,284 adult transplant recipients the following groups had increased risk of graft failure: younger and older recipients, increasing PRA (hazard ratio [HR],1.03-1.06], increasing BMI (HR, 1.04-1.62), previous kidney transplant (HR, 1.17-1.26), dialysis at the time of transplantation (HR, 1.39-1.51), hepatitis C infection (HR, 1.41-1.63), and educational level (HR, 1.05-1.42). Predictive criteria based on recipient characteristics could guide organ allocation, risk stratification, and patient expectations in planning kidney transplantation.

Glycopolymers Prepared by Ring-Opening Metathesis Polymerization Followed by Glycoconjugation Using a Triazole-Forming "Click" Reaction.

We describe a protocol for the preparation of glycopolymers derived from the ring-opening polymerization of a norbornene carboxylic acid derivative. Polymerization is followed by attachment of a linker and subsequent glycoconjugation via a triazole-forming azide-alkyne click reaction. The use of a protected amine-terminating agent allows for the attachment of a probe molecule such as a fluorescein dye. The syntheses of a neutral galactopolymer as well a polyanionic poly-3-O-sulfo-galactopolymer are described.

Effects of Parvovirus B19 Infection in Renal Transplant Recipients: A Retrospective Review of Three Cases.

Parvovirus B19 (PVB19) is a DNA virus which causes clinically relevant infection in renal transplant recipients (RTR) leading to significant morbidity. Manifestations include erythropoietin resistant anemia, proteinuria, and glomerulosclerosis in the allograft. Severe infection may require administration of intravenous immunoglobulin, reduction in immunosuppression and transfusions. The major challenge in managing and preventing the infection in RTR involves the act of balancing the decreased level of immunosuppression and the risk of rejection. The objective of this article is to understand the importance of PVB19 infection and its outcome in RTR. We reviewed the medical records of three RTR with confirmed PVB19 infection and recorded patient information including demographics, clinical and laboratory data, management, and outcome. The average time of occurrence of PVB19 infection as transplant was 8.6 weeks and they presented with symptomatic anemia. Elevated creatinine values were noted in two of them. Following treatment, anemia improved and creatinine values returned to baseline. One of them developed an early relapse and had to be treated once again similarly. We emphasize the importance of maintaining a high index of suspicion for PVB19 infection in patients with anemia in the posttransplant phase, especially in patients on higher doses of immunosuppressants. Early and proper treatment can prevent worsening clinical condition and possible effects on the allograft.

Pancreatic retransplantation is associated with poor allograft survival: an update of the United Network for Organ Sharing database.

UNLABELLED: The aim of the study was to assess outcomes of pancreas retransplantation versus primary pancreas transplantation. METHODS: Data from the United Network for Organ Sharing database on all adult (age, ≥18 years) subjects who received pancreas and kidney-pancreas transplants between 1996 and 2012 were analyzed (n = 20,854). The subjects were analyzed in the following 2 groups: retransplant (n = 1149) and primary transplant (n = 19,705). RESULTS: Kaplan-Meier analysis demonstrated significantly different patient survival (P < 0.0001) and death-censored graft survival (P < 0.0001) between the primary transplant versus retransplant subjects. Allograft survival was significantly poorer in the retransplantation group. Patient survival was greater in the retransplant group. CONCLUSIONS: The results of our study differ from previous studies, which showed similar allograft survival in primary and secondary pancreas transplants. Further studies may elucidate specific patients who will benefit from retransplantation. At the present time, it would appear that pancreas retransplantation is associated with poor graft survival and that retransplantation should not be considered for all patients with primary pancreatic allograft failure.

Anti-bacterial glycosyl triazoles - Identification of an N-acetylglucosamine derivative with bacteriostatic activity against Bacillus.

N-acetylglucosaminidases (GlcNAcases) play an important role in the remodeling and recycling of bacterial peptidoglycan. Inhibitors of bacterial GlcNAcases can serve as antibacterial agents and provide an opportunity for the development of new antibiotics. We report the synthesis of triazole derivatives of N-acetylglucosamine using a copper promoted azide-alkyne coupling reaction between 1-azido-N-acetylglucosamine and a small library of terminal alkynes prepared via the Ugi reaction. These compounds were evaluated for their ability to inhibit the growth of bacteria. Two compounds that show bacteriostatic activity against Bacillus were identified, with MIC values of approximately 60 µM in both cases. Bacillus subtilis cultured in the presence of sub-MIC amounts of the glycosyl triazole inhibitors exhibit an elongated phenotype characteristic of impaired cell division. This represents the first report of inhibitors of bacterial cell wall GlcNAcases that demonstrate inhibition of cell growth in whole cell assays.

An analysis of pancreas transplantation outcomes based on age groupings--an update of the UNOS database.

INTRODUCTION: Previously, increasing age has been a part of the exclusion criteria used when determining eligibility for a pancreas transplant. However, the analysis of pancreas transplantation outcomes based on age groupings has largely been based on single-center reports. METHODS: A UNOS database review of all adult pancreas and kidney-pancreas transplants between 1996 and 2012 was performed. Patients were divided into groups based on age categories: 18-29 (n = 1823), 30-39 (n = 7624), 40-49 (n = 7967), 50-59 (n = 3160), and ≥60 (n = 280). We compared survival outcomes and demographic variables between each age grouping. RESULTS: Of the 20 854 pancreas transplants, 3440 of the recipients were 50 yr of age or above. Graft survival was consistently the greatest in adults 40-49 yr of age. Graft survival was least in adults age 18-29 at one-, three-, and five-yr intervals. At 10- and 15-yr intervals, graft survival was the poorest in adults >60 yr old. Patient survival and age were found to be inversely proportional; as the patient population's age increased, survival decreased. CONCLUSION: Pancreas transplants performed in patients of increasing age demonstrate decreased patient and graft survival when compared to pancreas transplants in patients <50 yr of age.

The use of venous jump grafts in pancreatic transplantation - no difference in patient or allograft outcomes - an update of the UNOS database.

Venous jump grafts are used in pancreas transplantation to salvage a pancreas with a short portal vein or to facilitate an easier anastomosis. There have been no large studies evaluating the safety of venous jump grafts in pancreas transplantation. We analyzed the UNOS database to determine whether venous jump grafts are associated with graft loss or patient death. Data from UNOS on all adult pancreas transplant recipients 1996-2012 were analyzed. Venous extension grafts were used in 2657 cases; they were not in 18 124. Kaplan-Meier/product-limit estimates analysis demonstrated similar patient survival (p < 0.641) and death-censored graft survival (p < 0.351) at one, three, five,10, and 15 yr between subjects with and without venous jump grafts. There was a statistically significant difference in one-yr unadjusted patient survival between the venous extension graft (94.9%) and the no-venous extension graft (95.8%) groups (p < 0.045) and a borderline difference in one-yr graft survival between the venous extension graft (84.1%) and the no-venous extension graft (82.6%) groups (p < 0.055). There was no significant difference in patient survival or allograft survival at the three-, five-, 10-, and 15-yr intervals. The use of venous jump grafts is not associated with increased graft loss or mortality.

Extended-spectrum-beta-lactamase producing bacteria related urinary tract infection in renal transplant recipients and effect on allograft function.

BACKGROUND: Urinary tract infection (UTI) is a well-recognized early complication in renal transplant recipients (RTR) and can have significant bearing on their outcome. The recent rise in incidence of extended spectrum beta lactamase (ESBL) producing bacteria causing UTI among RTR poses new and significant challenges in terms of management and outcome. Our aim is to analyze the effect of ESBL producing bacteria causing UTI in these patients and its impact on allograft function. METHODS: We reviewed the medical records of 147 RTR who were followed at a tertiary care hospital affiliated transplant center between January 2007 and May 2013 and noted five RTR who developed episodes of ESBL producing bacteria related UTI during follow up. Multiple patient characteristics including demographics, immunosuppression, recurrences, allograft function and outcome were analyzed. RESULTS: Five patients (3.4%) out of 147 had ESBL producing bacteria related UTI. We found all patients to be above 60 years of age, with three out of five being females, and all five patients had diabetes mellitus. We identified a total of 37 episodes of UTI among these five patients during this period. Two of these patients had elevated creatinine values during the episodes of UTI and three of them developed bacteremia. Of the five patients, four of them had a favorable outcome except for one patient who developed persistent allograft dysfunction. CONCLUSION: RTR are at a higher risk for developing ESBL producing bacteria associated UTI. Early diagnosis along with appropriate and judicious use of antibiotics will ensure long term success in allograft and patient outcome.

Pancreas transplantation from donors after cardiac death: an update of the UNOS database.

OBJECTIVE: There is reluctance to use donation after cardiac death (DCD) organs for fear of worse outcomes due to increased warm ischemia time. Extensive evidence to confirm the quality of DCD pancreas transplants is not manifest. METHODS: A united network for organ sharing database review of pancreas transplants performed between 1996 and 2012 was conducted. We compared outcomes and all demographic variables between donors after cardiac death and donors after brain death in pancreas transplantation. RESULTS: There were 320 DCD pancreas transplants and 20,448 donation after brain death pancreas transplants performed in the United States between 1996 and 2012. There was no statistically significant difference in graft survival or patient survival in pancreas transplantation in DCD versus donation after brain death donors measured at 1-year, 3-year, 5-year, 10-year, and 15-year intervals. There was no significant difference between donor and recipient age, race, sex, and body mass index (BMI) between the groups. There was no significant difference between the recipient ethnicity or time on wait list between the groups. CONCLUSIONS: Pancreata procured by DCD have comparable outcomes to those procured after brain death. Donation after cardiac death pancreas transplant is a viable method of increasing the donor pool, decreasing wait list mortality, and improving the quality of life for type 1 diabetic patients.