The random phase approximation applied to ice

Standard density functionals without van der Waals interactions yield an unsatisfactory description of ice phases, specifically, high density phases occurring under pressure are too unstable compared to the common low density phase I$_h$ observed at ambient conditions. Although the description is improved by using functionals that include van der Waals interactions, the errors in relative volumes remain sizable. Here we assess the random phase approximation (RPA) for the correlation energy and compare our results to experimental data as well as diffusion Monte Carlo data for ice. The RPA yields a very balanced description for all considered phases, approaching the accuracy of diffusion Monte Carlo in relative energies and volumes. This opens a route towards a concise description of molecular water phases on surfaces and in cavities

Modified Hemagglutination Tests for COVID-19 Serology in Resource-Poor Settings: Ready for Prime-Time?

During the ongoing COVID-19 pandemic, serology has suffered several manufacturing and budget bottlenecks. Kode technology exposes exogenous antigens on the surface of cells; in the case of red blood cells, modified cells are called kodecytes, making antibody\u2013antigen reactions detectable by the old-fashioned hemagglutination test. In this commentary, we review evidence supporting the utility of SARS-CoV-2 Spike kodecytes for clinical diagnostic purposes and serosurveys in resource-poor settings

Sulfoglycolipids analogues as new molecules for tumor treatment

The sulfoglycolipids sulfoquinovosylacylglycerols(SQAG) are abundant sulfur-containing glycerolipids that are associated with photosynthetic organisms especially with a large number of marine algae. Their main structural feature is the anionic head group constituent sulfoquinovose, a derivative of glucose in which the 6-hydroxyl is replaced by a sulfonate group, \uf061-linked to the sn-3 position of a diacylglycerol1. Recently reported biological activities of SQAGs, including inhibitory effects on HIV-reverse transcriptase, and mammalian DNA polymerase, proliferation of some cancer cell lines, angiogenesis (especially when coupled with tumor radiotherapy), and apoptosis induction, make these compounds very attractive for their potential in cancer therapy. Also, extractive SQAG mixtures are known to inhibit in vitro TPA induced tumor promotion stage. To obtain new active compounds for cancer therapy by structural modification of natural SQAGs, SQAG analogues have been synthesized in which the sulfoquinovose moiety is linked to the 2 position of glycerol carrying acyl chains of different length. Similar compounds in fact, with a 6\u2019-hydroxyl instead of a 6\u2019-sulfonate (namely some glycoglycerolipid analogues), are known to be active as anti-tumor-promoters in TPA promoted carcinogenesis in vitro and in vivo experiments. A synthetic strategy has been used to selectively insert the proper chemical functionalities (i.e. sulfonate and acyl chains) at the desired positions of the previously prepared glucosylglycerol skeleton to obtain the target compounds. Biological evaluation of anti-tumor activities will be performed including the study of their chemopreventing potential

Electronic State Unfolding for Plane Waves: Energy Bands, Fermi Surfaces, and Spectral Functions

Present day computing facilities allow for first-principles density functional theory studies of complex physical and chemical phenomena. Often such calculations are linked to large supercells to adequately model the desired property. However, supercells are associated with small Brillouin zones in the reciprocal space, leading to folded electronic eigenstates that make the analysis and interpretation extremely challenging. Various techniques have been proposed and developed to reconstruct the electronic band structures of super cells unfolded into the reciprocal space of an ideal primitive cell. Here we propose an unfolding scheme embedded directly in the Vienna Ab initio Simulation Package (VASP) that requires modest computational resources and allows for an automatized mapping from the reciprocal space of the supercell to the primitive cell Brillouin zone. This algorithm can compute band structures, Fermi surfaces, and spectral functions by using an integrated postprocessing tool (bands4vasp). Here the method is applied to a selected variety of complex physical situations: the effect of doping on the band dispersion in the BaFe2(1-x)Ru2xAs2 superconductor, the interaction between adsorbates and polaronic states on the TiO2(110) surface, and the band splitting induced by noncollinear spin fluctuations in EuCd2As2

Diarylureas as antitumor agents

The diarylurea is a scaffold of great importance in medicinal chemistry as it is present in numerous heterocyclic compounds with antithrombotic, antimalarial, antibacterial, and anti-inflammatory properties. Some diarylureas, serine-threonine kinase or tyrosine kinase inhibitors, were recently reported in literature. The first to come into the market as an anticancer agent was sorafenib, followed by some others. In this review, we survey progress over the past 10 years in the development of new diarylureas as anticancer agents

Chemoenzymatic synthesis of sulfoquinovosylmonoacylglycerols (SQMG) as anti-tumor-promoters

During our search for new glycoglycerolipids active in cancer chemoprevention, in recent years we have synthesized a number of esters of 2-O-beta-D-glycosylglycerols in which the length, shape, number and position of the acyl chain, and the type of sugar (alpha\uf020and beta glucose or galactose) were varied. These compounds were found to be very active in inhibiting the tumor-promoting activity of the phorbol ester TPA both in in vitro and in in vivo tests, being such activities mainly influenced by the changes of the acyl chains length. Sulfoquinovosylacylglycerols are acylated sulfoglycolipids in which sulfoquinovose (6-deoxy-6-sulfo-glucose) is alpha-linked to the sn-3 position of glycerol. These compounds exhibit noteworthy biological activities, that make them very attractive for their use in cancer therapy. Here we report the synthesis of 6\u2019-sulfo-derivatives (SQMG) based on the skeleton of 2-O-beta-D-glucosylglycerol to which previously synthesized biologically active glucoglycerolipid analogues are related. A chemoenzymatic strategy has been used to selectively insert the proper chemical functionalities (i.e. acyl chain) at the desired position of glucosylglycerol to obtain the target compounds. Their potential as anti-tumor-promoters will be also discussed

Halogen bonding in the framework of classical force fields: The case of chlorine

Halogen bonding is nowadays a consolidated tool in chemistry. Only recently, the importance of halogen bonding has been demonstrated also in biological systems, owing to the presence of halogens in drugs. This interaction is due to the anisotropy of the electron density around the halogen that leads to the formation of the \u2018\u3c3-hole\u2019, which is responsible for the interaction with a nucleophile site. Unfortunately, classical force fields used in the study of ligand-receptor systems are not able to describe the \u2018\u3c3-hole\u2019. Here, we propose a pseudo-atom based methodology able to correctly describe halogen bonding involving chlorine using classical force field

X-ray constrained spin-coupled technique: Theoretical details and further assessment of the method

One of the well-established methods of modern quantum crystallography is undoubtedly the X-ray constrained wavefunction (XCW) approach, a technique that enables the determination of wavefunctions which not only minimize the energy of the system under examination, but also reproduce experimental X-ray diffraction data within the limit of the experimental errors. Initially proposed in the framework of the Hartree-Fock method, the strategy has been gradually extended to other techniques of quantum chemistry, but always remaining limited to a single-determinant ansatz for the wavefunction to extract. This limitation has been recently overcome through the development of the novel X-ray constrained spin-coupled (XCSC) approach [Genoni et al. (2018). Chem. Eur. J. 24, 15507-15511] which merges the XCW philosophy with the traditional spin-coupled strategy of valence bond theory. The main advantage of this new technique is the possibility of extracting traditional chemical descriptors (e.g. resonance structure weights) compatible with the experimental diffraction measurements, without the need to introduce information a priori or perform analyses a posteriori. This paper provides a detailed theoretical derivation of the fundamental equations at the basis of the XCSC method and also introduces a further advancement of its original version, mainly consisting in the use of molecular orbitals resulting from XCW calculations at the Hartree-Fock level to describe the inactive electrons in the XCSC computations. Furthermore, extensive test calculations, which have been performed by exploiting high-resolution X-ray diffraction data for salicylic acid and by adopting different basis sets, are presented and discussed. The computational tests have shown that the new technique does not suffer from particular convergence problems. Moreover, all the XCSC calculations provided resonance structure weights, spin-coupled orbitals and global electron densities slightly different from those resulting from the corresponding unconstrained computations. These discrepancies can be ascribed to the capability of the novel strategy to capture the information intrinsically contained in the experimental data used as external constraints

A valence bond description of the bromine halogen bond

A theoretical investigation on the nature of the halogen bond through a valence-bond approach has been carried out with two main goals: (a) finding further confirmations of already existing explanations on the physical origins of the halogen bond and (b) possibly enriching the current models with new details. To achieve these goals we have exploited the spin-coupled method and we have performed computations on RBr efNH3 dimers characterized by a different electron withdrawing power of substituent \uf8ffR to the bromine atom. The analysis of typical spin-coupled descriptors (eg, shapes and overlaps of the spin-coupled orbitals, weights of the spin-coupled structures) in the different cases and in function of the distance between the monomers allowed us to draw qualitative conclusions about the formation and the strength of the halogen bonds. In particular, the investigation not only confirmed the validity of already existing models (ie, \u3c3-hole and lump-hole models) but also highlighted interesting new features, such as the fact that the depletion of electron density around the bromine atom does not extend only toward the acceptor of the halogen bond, but also in the opposite direction (toward the substituent of the halogen), thus forming a sort of \u3c3-tunnel, rather than a simple \u3c3-hole