Developing deprotectase biocatalysts for synthesis.

Organic synthesis often requires multiple steps where a functional group (FG) is concealed from reaction by a protecting group (PG). Common PGs include N-carbobenzyloxy (Cbz or Z) of amines and tert-butyloxycarbonyl (OtBu) of acids. An essential step is the removal of the PG, but this often requires excess reagents, extensive time and can have low % yield. An overarching goal of biocatalysis is to use "green" or "enzymatic" methods to catalyse chemical transformations. One under-utilised approach is the use of "deprotectase" biocatalysts to selectively remove PGs from various organic substrates. The advantage of this methodology is the exquisite selectivity of the biocatalyst to only act on its target, leaving other FGs and PGs untouched. A number of deprotectase biocatalysts have been reported but they are not commonly used in mainstream synthetic routes. This study describes the construction of a cascade to deprotect doubly-protected amino acids. The well known Bacillus BS2 esterase was used to remove the OtBu PG from various amino acid substrates. The more obscure Sphingomonas Cbz-ase (amidohydrolase) was screened with a range of N-Cbz-modified amino acid substrates. We then combined both the BS2 and Cbz-ase together for a 1 pot, 2 step deprotection of the model substrate CBz-L-Phe OtBu to produce the free L-Phe. We also provide some insight into the residues involved in substrate recognition and catalysis using docked ligands in the crystal structure of BS2. Similarly, a structural model of the Cbz-ase identifies a potential di-metal binding site and reveals conserved active site residues. This new biocatalytic cascade should be further explored for its application in chemical synthesis.

Stretching the Bisalkyne Raman Spectral Palette Reveals a New Electrophilic Covalent Motif.

Small heteroaryl-diyne (Het-DY) tags with distinct vibrational frequencies, and physiologically relevant cLog P were designed for multiplexed bioorthogonal Raman imaging. Pd-Cu catalyzed coupling, combined with the use of Lei ligand, was shown to improve overall yields of the desired heterocoupled Het-DY tags, minimizing the production of homocoupled side-products. Spectral data were in agreement with the trends predicted by DFT calculations and systematic introduction of electron- rich/poor rings stretched the frequency limit of aryl-capped diynes (2209-2243 cm-1 ). The improved Log P of these Het-DY tags was evident from their diffuse distribution in cellular uptake studies and functionalizing tags with organelle markers allowed the acquisition of location-specific biological images. LC-MS- and NMR-based assays showed that some heteroaryl-capped internal alkynes are potential nucleophile traps with structure-dependent reactivity. These biocompatible Het-DY tags, equipped with covalent reactivity, open up new avenues for Raman bioorthogonal imaging.

A 3D graphene current collector boosts ultrahigh specific capacity in a highly uniform Prussian blue@graphene composite as a freestanding cathode for sodium ion batteries.

For the first time, a uniform graphene aerogel (GA) supported Prussian blue (PB) nanocube structure was synthesized by fitting the nanocube into the GA with a specific pore size and employing it in a freestanding sodium ion battery cathodic electrode. In this electrode, the graphene framework not only offers mechanical support, but also plays the role of a binder-free current collector. The theoretical specific capacity of Prussian blue was exceeded with an ultrahigh specific capacity of 214 mA h g-1 at 0.5 C. With the help of the electronic double layer capacitance of the graphene framework, this ultrahigh value can be achieved. We studied the influence of the mass loading of the PB nanocube on the specific capacity, finding that the GA-induced freestanding electrode has the potential to load a maximum of 72 wt% of the PB nanocube. Furthermore, we separated the capacitance and the capacity of the electrode through kinetic analysis, and discovered that the GA-induced carbon collector contributed to a surface-controlled capacitance, which accounted for 55% of the total capacity.

A general strategy for the functionalization of two-dimensional metal chalcogenides.

Two-dimensional (2D) metal chalcogenides (MC) such as MoS2 have been recognized as promising materials for near future applications. However, general strategies to functionalize them are still scarce, while the nature of functionalization still remains unclear. Herein, we demonstrate a simple and universal functionalization route through complexation reaction between the amino-containing organic agents and MCs. Degrees of functionalization are tunable by adjusting the organic group types and ratios. No further defects are introduced and the functionalized 2D MCs are dispersible in corresponding typical solvents. Both experimental results and geometry optimization calculations indicate that the grafting of functional groups through the coordination effect truly exist, while the surface properties and resulting photoelectric properties of 2D MCs are greatly altered. More intriguingly, our proposed functionalization process is demonstrated to be universal and can be applied to different MCs, thus opening new avenues for the application of 2D MCs.

Assessment of risk factors for increased resource utilization in kidney transplantation.

BACKGROUND: There are only a limited number of studies that have sought to identify patients at high risk for medication errors and subsequent adverse clinical outcomes. This study sought to identify risk factors for increased health care resource utilization in kidney transplant recipients based on drug-related problems and self-administered surveys. METHODS: In this prospective observational study, adult kidney transplant recipients seen in the transplant clinic between September and November 2015 were surveyed for self-reported demographics, medication adherence, and health status/outlook. Subsequently, patients were assessed for associations between survey results, pharmacist-derived drug-related problems, and health resource utilization over a minimum 6-mo follow-up period. Based on univariate associations, two risk cohorts were identified and compared for health care utilization using multivariable Poisson regression. RESULTS: A total of 237 patients were included, with a mean follow-up of 8 mo. From the patient survey data, Medicaid insured or self-rated poor health status were identified as a significant risk cohort. From pharmacist assessments, those who received incorrect medication or lacked appropriate follow-up medication monitoring were identified as a significant risk cohort (pharmacy errors). The Medicaid insured or self-rated poor health status cohort experienced 43% more total health care encounters (incident rate ratios [IRR] 1.43, 1.01-2.02) and 35% more transplant clinic visits (IRR 1.35, 1.03-1.77). The pharmacy errors cohort experienced 4.2 times the rate of total health care encounters (IRR 4.17, 1.55-11.2), 4.1 times the rate of hospital readmissions (IRR 4.09, 1.58-10.6), and 2.3 times the rate of transplant clinic visits (IRR 2.31, 1.04-5.11). CONCLUSIONS: Medicaid insurance, self-rated poor health status, and errors in the medication regimen or monitoring were significant risk factors for increased health care utilization in kidney transplant recipients. Further research is warranted to validate these potential risk factors, determine the long-term impact on graft/patient survival, and assess the mutability of these risks through prospective identification and intervention.

Expanding the endoscopic transpterygoid corridor to the petroclival region: anatomical study and volumetric comparative analysis.

OBJECTIVE The endoscopic endonasal transmaxillary transpterygoid (TMTP) approach has been the gateway for lateral skull base exposure. Removal of the cartilaginous eustachian tube (ET) and lateral mobilization of the internal carotid artery (ICA) are technically demanding adjunctive steps that are used to access the petroclival region. The gained expansion of the deep working corridor provided by these maneuvers has yet to be quantified. METHODS The TMTP approach with cartilaginous ET removal and ICA mobilization was performed in 5 adult cadaveric heads (10 sides). Accessible portions of the petrous apex were drilled during the following 3 stages: 1) before ET removal, 2) after ET removal but before ICA mobilization, and 3) after ET removal and ICA repositioning. Resection volumes were calculated using 3D reconstructions generated from thin-slice CT scans obtained before and after each step of the dissection. RESULTS The average petrous temporal bone resection volumes at each stage were 0.21 cm3, 0.71 cm3, and 1.32 cm3 (p < 0.05, paired t-test). Without ET removal, inferior and superior access to the petrous apex was limited. Furthermore, without ICA mobilization, drilling was confined to the inferior two-thirds of the petrous apex. After mobilization, the resection was extended superiorly through the upper extent of the petrous apex. CONCLUSIONS The transpterygoid corridor to the petroclival region is maximally expanded by the resection of the cartilaginous ET and mobilization of the paraclival ICA. These added maneuvers expanded the deep window almost 6 times and provided more lateral access to the petroclival region with a maximum volume of 1.5 cm3. This may result in the ability to resect small-to-moderate sized intradural petroclival lesions up to that volume. Larger lesions may better be approached through an open transcranial approach.

Transposition of the paraclival carotid artery: a novel concept of self-retaining vascular retraction during endoscopic endonasal skull base surgery technical report.

BACKGROUND: Fixed retraction of the internal carotid artery (ICA) has previously been described for use during transcranial microscopic surgery. We report the novel use of a self-retaining microvascular retractor for static repositioning and protection of the ICA during expanded endonasal endoscopic approaches to the paramedian skull base. METHODS: The transmaxillary, transpterygoid approach was performed in five cadaver heads (ten sides). The self-retaining microvascular retractor was used to laterally reposition the pterygopalatine fossa contents during exposure of the pterygoid base/plates and the paraclival ICA to expose the petrous apex. Maximum ICA retraction distance was measured in the x-axis for all ten sides. RESULTS: The average horizontal distance of ICA retraction measured at the mid-paraclival segment for all ten sides was 4.75 mm. In all cases, the carotid artery was repositioned without injury to the vessel or disruption of the surrounding neurovascular structures. CONCLUSIONS: Static repositioning of the ICA and other delicate neurovascular structures was effectively performed during endonasal, endoscopic cadaveric surgery of the skull base and has potential merits in live patients.

Cervical disc arthroplasty.

This technology overview addressed four questions that compared the difference in outcomes between patients undergoing cervical disc arthroplasty with patients undergoing anterior cervical diskectomy fusion. Most studies did not either report or conduct the appropriate statistical analyses to examine predictive characteristics in patients with successful clinical outcomes. Most studies were inconclusive or unreliable regarding clinical outcomes and revision and/or complication rates in patients who present with neck and/or arm pain. No significant difference in the length of hospital stay was reported; however, two studies included in the overview reported that patients treated with cervical disc arthroplasty returned to work in significantly fewer days (range, 14 to 16 days) than did patients treated with anterior cervical diskectomy fusion.

Effects of acute ethanol or amphetamine administration on the acoustic startle response and prepulse inhibition in adolescent and adult rats.

RATIONALE: Adolescents differ from adults in their sensitivity to a variety of psychoactive drugs. For example, adolescent rats are less sensitive to locomotor stimulant and stereotypic effects of amphetamine as well as to motor-impairing and hypnotic effects of ethanol while more sensitive to ethanol-induced disruption of brain plasticity. OBJECTIVE: The current study further explored age differences in psychopharmacological sensitivity by examining the effects of d-amphetamine (1.0 and 4.0 mg/kg) or ethanol (0.5, 1.0 and 1.5 g/kg) given interperitoneally on the acoustic startle response (ASR) and prepulse inhibition (PPI) in male adolescent and adult Sprague-Dawley rats. MATERIALS AND METHODS: The animals were given five startle trials (120 dB for 40 ms) before semi-randomized presentation of 12 startle trials interspersed with ten trials at each prepulse intensity (40 ms pulse of 5, 10, or 20 dB above background; 100 ms before the startle stimulus). RESULTS: Adolescent controls showed significantly less PPI than adults, replicating previous ontogenetic findings. The higher dose of amphetamine disrupted PPI in adult but not in adolescent animals, extending previous reports of an adolescent insensitivity to amphetamine to include this measure of sensorimotor gating. Ethanol exposure failed to alter PPI at either age, although both the 1.0 and 1.5 g/kg doses of ethanol significantly suppressed the magnitude of the ASR at both ages, potentially reflecting sedative or anxiolytic effects. CONCLUSION: These data provide further evidence of the relative insensitivity of adolescent animals to amphetamine, although no age effects were found in terms of ethanol sensitivity using these measures of startle and sensorimotor gating.