Metal ions with radical centers in their coordination sphere are key participants in biological and catalytic processes. In the present study, we describe the synthesis of the cAAC:ZnCl2 adduct (1) using a cyclic alkylaminocarbene (cAAC) as donor ligand. Compound 1 was treated with 2 equiv of KC8 and LiB(sec-Bu)3H to yield a deep blue-colored dicarbene zinc compound (cAAC)2Zn (2) and the colorless hydrogenated zinc compound (cAACH)2Zn (3), respectively. Compounds 2 and 3 were well characterized by spectroscopic methods and single-crystal X-ray structural analysis. Density functional theory calculations were performed for 2 which indicate that this molecule possesses a singlet biradicaloid character. Moreover, we show the application of 2 in CO2 activation, which yields a zwitterionic cAAC·CO2 adduct.

The bisadduct (cAAC)2NiIICl2 [1; cAAC = cyclic (alkyl)(amino)carbene] was directly synthesized by treating cAAC with NiCl2. Compound 1 was reduced to (cAAC)2Ni0 (2) by using lithium diisopropylamide or KC8. Crystals of 2 were stable under an inert gas for several months and decomposed upon heating above 165 °C. On the basis of the calculated natural bond orbital charge values of the nickel atom in 2, the oxidation state of nickel was determined to be between NiI and Ni0 (+0.34). Theoretical calculations suggested a closed‐shell singlet electronic configuration of 2 with little biradical character. Ab initio multiconfigurational C(R)ASSCF/CASPT2 calculations predicted a closed‐shell singlet electronic configuration (Ni0), whereas excited spin states possessed NiI character with unpaired electrons on neighboring carbon atoms. The catalytic activity of complex 2 was investigated for the homocoupling of various unactivated aryl chlorides/fluorides. The biaryls were obtained in good yields at moderate temperature. Theoretical studies showed that an intermediate containing NiIII was more favored than one with NiIV.

BackgroundCoronary artery anomalies (CAAs) are rare disorders of coronary anatomy with varied clinical presentations. There are widespread geographic variations in incidence and patterns of these anomalies, with limited data from North Indian population. We performed a retrospective study to evaluate the incidence, characteristics and atherosclerotic involvement of CAAs in adult population undergoing catheter coronary angiography.MethodsSerial coronary angiographies performed at our institution over a period of 2.5 years (from January 2017 to June 2019) were retrospectively analyzed. We identified patients with anomalous coronaries and studied their clinical characteristics and angiographic profiles.ResultsAmong 3,233 coronary angiograms analyzed, CAAs were found in 99 patients with an incidence of 3.06%. Mean age of the patients was 56.2 ± 12.9 years (range: 20 - 86 years), with 74.75% being males and 25.25% females. Split right coronary artery (RCA) was the most common coronary anomaly, being seen in 27 patients; with an angiographic incidence of 0.84%. Dual left anterior descending artery (LAD) was the second most common anomaly and was seen in 22 cases with an angiographic incidence of 0.68%. Absent left main trunk was noted in 14 patients (0.43%). Ectopic origin of RCA from left sinus was seen in 12 patients (0.37%), while ectopic origin of RCA from ascending aorta was seen in four patients (0.12%). Ectopic origin of left circumflex artery (LCX) from right sinus or RCA was noted in 13 patients (0.40%). One patient (0.03%) had a superdominant LAD supplying the posterior descending artery (PDA). Coronary artery fistulae were seen in six patients (0.18%). Significant coronary artery disease (CAD) was seen in 89 of 268 (33.21%) normal vessels, whereas it was seen in 56 of 114 (49.12%) of anomalous vessels. This difference was statistically significant (P = 0.003).ConclusionsThe incidence of CAAs in our study was slightly higher than many of the previous angiographic series. The patterns of coronary anomalies in our study were different from most of the previous studies. Our study had higher incidence of atherosclerotic involvement of anomalous vessels as compared to normal vessels.

Mucopolysaccharidosis IIIA is a fatal neurodegenerative disease that typically manifests itself in childhood and is caused by mutations in the gene for the lysosomal enzyme sulfamidase. The first structure of this enzyme is presented, which provides insight into the molecular basis of disease-causing mutations, and the enzymatic mechanism is proposed.

The chemistry of stable metalylenes (the heavier group 14 element analogues of carbenes) is an intriguing target of main group chemistry due to their synthetic potential and industrial application. In the present study, we report on the utilization of an abnormal N-heterocyclic carbene (aNHC) and a cyclic alkyl-amino carbene (cAAC) as a Lewis base for the syntheses of compounds aNHC·SiCl2 (3), aNHC·SnCl2 (4), and cAAC·SnCl2 (5). The synthesis of silylene 3 involved the ligand-substitution reaction between NHC·SiCl2 and an aNHC. However, compounds 4 and 5 were synthesized by the reactions of aNHC and cAAC with SnCl2 in the molar ratio of 1:1. Compounds 3–5 are well-characterized with various spectroscopic methods and single-crystal X-ray structural analysis.

Single-crystal X-ray diffraction (XRD) is often considered the gold standard in analytical chemistry, as it allows element identification as well as determination of atom connectivity and the solid-state structure of completely unknown samples. Element assignment is based on the number of electrons of an atom, so that a distinction of neighboring heavier elements in the periodic table by XRD is often difficult. A computationally efficient procedure for aspherical-atom least-squares refinement of conventional diffraction data of organometallic compounds is proposed. The iterative procedure is conceptually similar to Hirshfeld-atom refinement (Acta Crystallogr. Sect. A- 2008, 64, 383-393; IUCrJ. 2014, 1,61-79), but it relies on tabulated invariom scattering factors (Acta Crystallogr. Sect. B- 2013, 69, 91-104) and the Hansen/Coppens multipole model; disordered structures can be handled as well. Five linear-coordinate 3d metal complexes, for which the wrong element is found if standard independent-atom model scattering factors are relied upon, are studied, and it is shown that only aspherical-atom scattering factors allow a reliable assignment. The influence of anomalous dispersion in identifying the correct element is investigated and discussed.

Background: Coronary artery disease is the leading cause of mortality in India. There is scarcity of data on demographic profile and outcomes of acute coronary syndrome (ACS) in low socioeconomic status (SES) population of India. Objectives: This study was undertaken to determine the clinical presentation, management strategies, and in-hospital outcomes of ACS in low SES population. Methods: We conducted 1-year prospective observational cohort study of ACS patients admitted at Employees State Insurance Corporation unit of our tertiary care cardiac center. Clinical parameters, management strategies, and in-hospital outcomes of 621 patients enrolled during the study period from February 2015 to January 2016 were studied. Results: Mean age of patients was 56.06 ± 11.29 years. Majority (62%) of the patients had ST elevation myocardial infarction (STEMI), whereas Non-ST elevation acute coronary syndrome (NSTE-ACS) was seen in 38% of the patients. Median time from symptom onset to hospital admission was 285 min with wide range from 105 to 1765 min. Coronary angiography was performed in 81% of patient population. Single-vessel disease (SVD) was the most common pattern (seen in 43.3%) of coronary artery involvement with left anterior descending coronary artery (LAD) being the most frequently involved vessel (62.8%). Pharmaco-invasive approach was the preferred strategy. Overall percutaneous coronary intervention (PCI) rates were 59.1% (62.1% in STEMI and 54.2% in NSTE-ACS). Overall in-hospital mortality was 3.2%, being significantly higher in STEMI (4.2%) as compared with NSTE-ACS (1.7%). Conclusions: With implementation of evidence-based pharmacotherapy and interventions, outcomes comparable with developed countries can be achieved even in low SES populations of developing world.

Isocitrate dehydrogenase catalyzes the first oxidative and decarboxylation steps in the citric acid cycle. It also lies at a crucial bifurcation point between CO2-generating steps in the cycle and carbon-conserving steps in the glyoxylate bypass. Hence, the enzyme is a focus of regulation. The bacterial enzyme is typically dependent on the coenzyme nicotinamide adenine dinucleotide phosphate. The monomeric enzyme from Corynebacterium glutamicum is highly specific towards this coenzyme and the substrate isocitrate while retaining a high overall efficiency. Here, a 1.9 Å resolution crystal structure of the enzyme in complex with its coenzyme and the cofactor Mg2+ is reported. Coenzyme specificity is mediated by interactions with the negatively charged 2'-phosphate group, which is surrounded by the side chains of two arginines, one histidine and, via a water, one lysine residue, forming ion pairs and hydrogen bonds. Comparison with a previous apoenzyme structure indicates that the binding site is essentially preconfigured for coenzyme binding. In a second enzyme molecule in the asymmetric unit negatively charged aspartate and glutamate residues from a symmetry-related enzyme molecule interact with the positively charged arginines, abolishing coenzyme binding. The holoenzyme from C. glutamicum displays a 36° interdomain hinge-opening movement relative to the only previous holoenzyme structure of the monomeric enzyme: that from Azotobacter vinelandii. As a result, the active site is not blocked by the bound coenzyme as in the closed conformation of the latter, but is accessible to the substrate isocitrate. However, the substrate-binding site is disrupted in the open conformation. Hinge points could be pinpointed for the two molecules in the same crystal, which show a 13° hinge-bending movement relative to each other. One of the two pairs of hinge residues is intimately flanked on both sides by the isocitrate-binding site. This suggests that binding of a relatively small substrate (or its competitive inhibitors) in tight proximity to a hinge point could lead to large conformational changes leading to a closed, presumably catalytically active (or inactive), conformation. It is possible that the small-molecule concerted inhibitors glyoxylate and oxaloacetate similarly bind close to the hinge, leading to an inactive conformation of the enzyme.