Duplication cyst in adult cases: a journey from diagnosis to treatment.

Duplication cysts are rare congenital abnormalities of the alimentary tract, typically manifesting symptoms in the first 2 years but uncommon in adults. Medical data on duplication cysts is scarce in Vietnam's Mekong Delta region. These two adult cases aim to provide fundamental knowledge, clinical characteristics, diagnosis, risks, complications, surgical and observational treatment methods, and future bilateral tumor research. Case 1: A 21-year-old male with intestinal obstruction symptoms. Computed tomography (CT)-scan revealed a strangulated small bowel obstruction with ischemia. Laparotomy discovered a twisted ileal duplication cyst causing necrosis in ~30 cm of the small intestine. Case 2: A 34-year-old woman hospitalized for right lower quadrant pain. CT-scan showed a cystic structure protruding into the ascending colon lumen. She underwent a laparoscopic right hemicolectomy, and an ascending colonic cyst was found in the specimen. Conclusions: Duplication cysts are rare anomalies, especially in adults. Comprehending and acquiring knowledge ensures prompt diagnosis and appropriate treatment.

A Cross-Sectional Study Investigating Clinical Features, Brain Imaging, and Treatment Efficacy in Patients with Cerebral Venous Thrombosis in the Mekong Delta, Vietnam.

Background: Cerebral venous thrombosis (CVT) is a challenging condition with potential long-term consequences, but it is also a treatable disorder that offers the possibility of complete recovery. This study was conducted to comprehensively investigate the clinical features, brain imaging findings, and treatment outcomes of patients diagnosed with cerebral venous thrombosis. Materials and Methods: Conducted as a cross-sectional descriptive study, patients diagnosed with cerebral venous thrombosis were enrolled at Can Tho Central General Hospital between January 2021 and June 2022. Results: Notably, a substantial proportion of patients (83.4%) exhibited signs of brain damage, with intracranial hemorrhage (50%), brain infarction (30.9%), subarachnoid hemorrhage (16.6%), and hemorrhagic infarct (4.7%) being the predominant findings. Thrombosis primarily affected the superior sagittal sinus (85.7%), transverse sinus (52.4%), and sigmoid sinus (42.8%). All patients received anticoagulation treatment, resulting in a favorable recovery upon hospital discharge for the majority (90.5%), while a small percentage (9.5%) experienced critical illness or death. Conclusion: Our study on cerebral venous thrombosis found diverse clinical presentations, primarily headache. Intracranial hemorrhage was common, affecting superior sagittal, transverse, and sigmoid sinuses. Most patients achieved favorable recoveries with anticoagulation treatment, emphasizing early intervention's importance.

Clinical Features and the Outcome Evaluations of Keloid and Hypertrophic Scar Treatment with Triamcinolone Injection in Mekong Delta, Vietnam - A Cross-Sectional Study.

Background: Excessive scarring is a common problem that can have significant cosmetic and psychological consequences for patients. Intralesional injection therapy, such as the use of triamcinolone, has emerged as an effective treatment option for hypertrophic scars. The objective of this study was to describe the morphological features of hypertrophic scars, categorize them, and evaluate the efficacy of triamcinolone injection therapy in treating these scars. Materials and Methods: A cross-sectional descriptive study of 80 patients with hypertrophic scars treated with triamcinolone intralesional injection at Can Tho University of Medicine and Pharmacy Hospital from 5/2018 to 5/2021. Results: There were 80 patients in all, with a male/female ratio of 1/1.05 and a median age of 15-35. There were 129 scars in all, with scar age >1 year accounting for 83%, keloid scars accounting for 64%, and hypertrophic scars accounting for the remaining 36%. Scars are most commonly seen on the trunk, accounting for 53.5% of all scars, particularly on the anterior chest wall. When the source of scars was discovered, trauma and acne accounted for 24% and 23%, respectively, while the rest were predominantly spontaneous scars, accounting for 49%. Scarring and discomfort of mild to moderate severity were common clinical symptoms; scars larger than 5cm in size had more symptoms than scars smaller than 5cm. Prior to the therapy, the mean Vancouver Score Scale-VSS was 6.55±2.13. After 24 weeks of the therapy, 96.7% of patients had entirely improved itching symptoms, 75% had completely improved pain, and 25% still had minimal pain. After therapy, the mean Vancouver Score Scale-VSS was 2.55±1.81 (p<0.05). At week 24, 3.75% of patients experienced skin shrinkage, 3.75% experienced depigmentation, and 13.75% experienced vasodilation. Conclusion: Triamcinolone intralesional injection should be utilized as a first-line therapy for hypertrophic scarring.

Pharmacist-Led Interventions to Reduce Drug-Related Problems in Prescribing for Pediatric Outpatients in a Developing Country: A Randomized Controlled Trial.

OBJECTIVE: To evaluate a pharmacist-led intervention's effectiveness in reducing drug-related problems (DRPs ( related to prescriptions for pediatric outpatients. METHODS: We conducted a randomized controlled trial. We recruited and randomly assigned 31 physicians to control or intervention groups. We collected 775 prescriptions (375 from the control group and 400 from the intervention group) at the start. For 3 weeks, intervention physicians received additional information and meetings with pharmacists in addition to the usual practices of the hospital. We then collected prescriptions at the end of the study. We classified DRPs, based on reliable references (Supplemental Table S1) at baseline and endpoint (a week after the intervention). The primary outcome was the proportion of prescriptions with DRPs, and secondary outcomes were the proportions of prescriptions with specific DRP types. RESULTS: The influence of the intervention on general DRPs and specific DRPs was the study's main finding. The pharmacist-led intervention helped reduce the prescriptions with DRPs proportion in the intervention group to 41.0%, compared with 49.3% in the control group (p < 0.05). The DRPs proportion related to the timing of administration relative to meals, unlike the other DRP types, increased in the control group (from 31.7% to 34.9%) and decreased in the intervention group (from 31.3% to 25.3%), with a significant difference between the 2 groups at endpoint (p < 0.01). Patients aged >2 to ≤6 years (OR, 1.871; 95% CI, 1.340-2.613) and receiving ≥5 drugs (OR, 5.037; 95% CI, 2.472-10.261) were at greater risk of experiencing DRPs related to prescribing. CONCLUSIONS: A pharmacist-led intervention improved DRP occurrence related to physicians' prescribing. Pharmacists could be involved in in-depth research with physicians in the prescribing process to provide tailored interventions.

Single Nucleotide Polymorphisms of FAM13A Gene in Chronic Obstructive Pulmonary Disease-A Case Control Study in Vietnam.

BACKGROUND: In 2018, GOLD addressed the issues of genotypes associated with risk factors for COPD. The genome-wide association study (GWAS) demonstrated an association between COPD and several genetic variants of single nucleotide polymorphisms (SNPs) of the FAM13A gene with the risk of COPD. OBJECTIVE: To study the single nucleotide polymorphisms rs2869967 and rs17014601 of the FAM13A gene in chronic obstructive pulmonary disease. Subjects and research methods: 80 subjects diagnosed with COPD and 80 subjects determined not to have COPD according to GOLD 2020 criteria; the subjects were clinically examined, interviewed, and identified as possessing single nucleotide polymorphisms using the sanger sequencing method on whole blood samples. RESULTS: The male/female ratio of the patient group and the control group was 79/1 and 39/1, respectively. The percentages of C and T alleles of rs2869967 in COPD patients were 50.6% and 49.4%, respectively. The percentages of C and T alleles of rs17014601 in COPD patients were 31.9% and 68.1%, respectively. At rs17014601, the ratio values of alleles T and C in the disease group and the control group were markedly different, making them statistically reliable (p = 0.031). The rate of CT genotype in the group of patients was considerably higher than that of the control group. The TT homozygous genotype had a lower risk of COPD compared with the other genotypes in the dominant model (ORTT/(CC + CT) = 0.441; CI95% = 0.233-0.833); this difference was statistically significant (p = 0.012). CONCLUSIONS: With rs17014601, it is characteristic that the frequency of the T allele appears more than the C allele, and the CT heterozygous phenotype accounts for the highest proportion in rs17014601 and rs2869967 recorded in COPD patients. There is an association between the genetic variant of the SNP FAM13A-rs17014601 and the risk of COPD.

FAM3C in circulating tumor-derived extracellular vesicles promotes non-small cell lung cancer growth in secondary sites.

Rationale: Metastasis is a complex process with a molecular underpinning that remains unclear. We hypothesize that cargo proteins conducted by extracellular vesicles (EVs) released from tumors may confer growth and metastasis potential on recipient cells. Here, we report that a cytokine-like secreted protein, FAM3C, contributes to late-stage lung tumor progression. Methods: EV protein profiling was conducted with an unbiased proteomic mass spectrometry analysis on non-small cell lung cancer (NSCLC) and normal lung fibroblast cell lines. Expression of FAM3C was confirmed in a panel of NSCLC cell lines, and correlated to the invasive and metastatic potentials. Functional phenotype of endogenous FAM3C and tumor-derived EVs (TDEs) were further investigated using various biological approaches in RNA and protein levels. Metastasis potential of TDEs secreted by FAM3C-overexpressing carcinoma cells was validated in mouse models. Results: Transcriptomic meta-analysis of pan-cancer datasets confirmed the overexpression of FAM3C - a gene encoding for interleukin-like EMT inducer (ILEI) - in NSCLC tumors, with strong association with poor patient prognosis and cancer metastasis. Aberrant expression of FAM3C in lung carcinoma cells enhances cellular transformation and promotes distant lung tumor colonization. In addition, higher FAM3C concentrations were detected in EVs extracted from plasma samples of NSCLC patients compared to those of healthy subjects. More importantly, we defined a hitherto-unknown mode of microenvironmental crosstalk involving FAM3C in EVs, whereby the delivery and uptake of FAM3C via TDEs enhances oncogenic signaling - in recipient cells that phenocopies the cell-endogenous overexpression of FAM3C. The oncogenicity transduced by FAM3C is executed via a novel interaction with the Ras-related protein RalA, triggering the downstream activation of the Src/Stat3 signaling cascade. Conclusions: Our study describes a novel mechanism for FAM3C-driven carcinogenesis and shed light on EV FAM3C as a driver for metastatic lung tumors that could be exploited for cancer therapeutics.

Structural investigation of human cystine/glutamate antiporter system xc - (Sxc -) using homology modeling and molecular dynamics.

The cystine/glutamate antiporter system xc - (Sxc -) belongs to the SLC7 family of plasma membrane transporters. It exports intracellular glutamate along the latter's concentration gradient as a driving force for cellular uptake of cystine. Once imported, cystine is mainly used for the production of glutathione, a tripeptide thiol crucial in maintenance of redox homeostasis and protection of cells against oxidative stress. Overexpression of Sxc - has been found in several cancer cells, where it is thought to counteract the increased oxidative stress. In addition, Sxc - is important in the central nervous system, playing a complex role in regulating glutamatergic neurotransmission and glutamate toxicity. Accordingly, this transporter is considered a potential target for the treatment of cancer as well as neurodegenerative diseases. Till now, no specific inhibitors are available. We herein present four conformations of Sxc - along its transport pathway, obtained using multi-template homology modeling and refined by means of Molecular Dynamics. Comparison with a very recently released cryo-EM structure revealed an excellent agreement with our inward-open conformation. Intriguingly, our models contain a structured N-terminal domain that is unresolved in the experimental structures and is thought to play a gating role in the transport mechanism of other SLC7 family members. In contrast to the inward-open model, there is no direct experimental counterpart for the other three conformations we obtained, although they are in fair agreement with the other stages of the transport mechanism seen in other SLC7 transporters. Therefore, our models open the prospect for targeting alternative Sxc - conformations in structure-based drug design efforts.

Medication Adherence in Vietnamese Patients with Cardiovascular and Endocrine-Metabolic Diseases.

(1) Background: COVID-19 has significantly affected the quality of life and the medication adherence of patients with chronic diseases. Attitudes towards the disease and preventive measures are the things that need to be considered for patient adherence to medication during the COVID-19 pandemic. We aimed to evaluate the rate and compare the medication adherence and the impact of the COVID-19 pandemic on medication adherence in Vietnamese patients with cardiovascular and endocrine−metabolic diseases. (2) Methods: A cross-sectional study was conducted on outpatients having chronic diseases such as cardiovascular or/and endocrine−metabolic diseases in some southern provinces in Vietnam. In each group of patients, medication adherence was measured and assessed with the General Medication Adherence Scale (GMAS), adjusted and validated in Vietnam. In addition, the study also investigated attitudes and practices to prevent COVID-19. (3) Results: Out of 1444 patients in our study, the level of adherence was recorded in 867 cases, accounting for 61.1%. The group of patients with only cardiovascular disease and patients with only endocrine−metabolic disease had relatively similar compliance rates of 62 and 61.1%, respectively. The leading cause of non-adherence to treatment in all three groups of patients in the study, as assessed by the GMAS, was non-adherence due to financial constraints. Our study showed that 71.6% of patients felt anxious when going to the hospital for a medical examination. However, only 53.7% identified the COVID-19 pandemic as obstructing treatment follow-up visits. The research results showed that the COVID-19 epidemic influences the patient's psychology with regard to re-examination and treatment adherence, with p coefficients of 0.003 and <0.001, respectively. (4) Conclusion: Medication adherence rates in two disease groups are close, and financial constraint is the fundamental reason for medication non-adherence. Regulatory agencies must take care of people's welfare to improve adherence in the epidemic context.

Medication Adherence and Belief about Medication among Vietnamese Patients with Chronic Cardiovascular Diseases within the Context of Implementing Measures to Prevent COVID-19.

BACKGROUND: Long-term adherence is crucial for optimal treatment outcomes in chronic cardiovascular diseases (CVDs), especially throughout the COVID-19 wide-spreading periods, making patients with chronic CVDs vulnerable subjects. AIM: To investigate the relationship between the characteristics, beliefs about prescribed medication, COVID-19 prevention measures, and medication adherence among patients with chronic CVDs. METHODS: This is a cross-sectional study of outpatients with chronic CVDs in Southern Vietnam. The specific parts regarding the Beliefs about Medicines Questionnaires (BMQ-Specific) and the General Medication Adherence Scale (GMAS) were applied to assess the beliefs about and adherence to medication. The implementation measures to prevent COVID-19 in patients were evaluated according to the 5K message (facemask, disinfection, distance, no gathering, and health declaration) of the Vietnam Ministry of Health. A multivariable logistic regression with the Backward elimination (Wald) method was used to identify the associated factors of medication adherence. RESULTS: A slightly higher score in BMQ-Necessity compared to BMQ-Concerns was observed. A total of 40.7% of patients were recorded as having not adhered to their medications. Patients' behavior was most frequently self-reported by explaining their non-adherence (34.7%). Statistical associations were found between rural living place, unemployment status, no or only one measure(s) of COVID-19 prevention application, and medication adherence. CONCLUSION: During the COVID-19 spreading stage, patients generally showed a positive belief about medication when they rated the importance of taking it higher than its side effects. The data analysis suggested that rather than patients' beliefs, the clinicians should consider the patient factors, including living place, employment, and the number of epidemic preventive measures applied for guiding the target patients for improving medication adherence.

Targeting codon 158 p53-mutant cancers via the induction of p53 acetylation.

Gain of function (GOF) DNA binding domain (DBD) mutations of TP53 upregulate chromatin regulatory genes that promote genome-wide histone methylation and acetylation. Here, we therapeutically exploit the oncogenic GOF mechanisms of p53 codon 158 (Arg158) mutation, a DBD mutant found to be prevalent in lung carcinomas. Using high throughput compound screening and combination analyses, we uncover that acetylating mutp53R158G could render cancers susceptible to cisplatin-induced DNA stress. Acetylation of mutp53R158G alters DNA binding motifs and upregulates TRAIP, a RING domain-containing E3 ubiquitin ligase which dephosphorylates IĸB and impedes nuclear translocation of RelA (p65), thus repressing oncogenic nuclear factor kappa-B (NF-ĸB) signaling and inducing apoptosis. Given that this mechanism of cytotoxic vulnerability appears inapt in p53 wild-type (WT) or other hotspot GOF mutp53 cells, our work provides a therapeutic opportunity specific to Arg158-mutp53 tumors utilizing a regimen consisting of DNA-damaging agents and mutp53 acetylators, which is currently being pursued clinically.

A common MET polymorphism harnesses HER2 signaling to drive aggressive squamous cell carcinoma.

c-MET receptors are activated in cancers through genomic events like tyrosine kinase domain mutations, juxtamembrane splicing mutation and amplified copy numbers, which can be inhibited by c-MET small molecule inhibitors. Here, we discover that the most common polymorphism known to affect MET gene (N375S), involving the semaphorin domain, confers exquisite binding affinity for HER2 and enables METN375S to interact with HER2 in a ligand-independent fashion. The resultant METN375S/HER2 dimer transduces potent proliferative, pro-invasive and pro-metastatic cues through the HER2 signaling axis to drive aggressive squamous cell carcinomas of the head and neck (HNSCC) and lung (LUSC), and is associated with poor prognosis. Accordingly, HER2 blockers, but not c-MET inhibitors, are paradoxically effective at restraining in vivo and in vitro models expressing METN375S. These results establish METN375S as a biologically distinct and clinically actionable molecular subset of SCCs that are uniquely amenable to HER2 blocking therapies.

Impact of the Astaxanthin, Betanin, and EGCG Compounds on Small Oligomers of Amyloid Aß40 Peptide.

There is experimental evidence that the astaxanthin, betanin, and epigallocatechin-3-gallate (EGCG) compounds slow down the aggregation kinetics and the toxicity of the amyloid-ß (Aß) peptide. How these inhibitors affect the self-assembly at the atomic level remains elusive. To address this issue, we have performed for each ligand atomistic replica exchange molecular dynamic (REMD) simulations in an explicit solvent of the Aß11-40 trimer from the U-shape conformation and MD simulations starting from Aß1-40 dimer and tetramer structures characterized by different intra- and interpeptide conformations. We find that the three ligands have similar binding free energies on small Aß40 oligomers but very distinct transient binding sites that will affect the aggregation of larger assemblies and fibril elongation of the Aß40 peptide.

Structural Investigation of Human Prolactin Receptor Transmembrane Domain Homodimerization in a Membrane Environment through Multiscale Simulations.

It is well established that prolactin (PRL) and its receptor (PRLR) are associated with hundreds of biological functions. They have been postulated to be linked to breast and prostate cancers, and PRLR signaling has attracted considerable medical and pharmaceutical interest in the development of compounds targeting PRLR. Dimerization of the receptor through its transmembrane (TM) domain is a key step for understanding its signaling and related issues. Our multiscale simulation results revealed that its TM domain can form dimers in a membrane environment with distinct states stabilized by different residue motifs. On the basis of the simulated data, an activation mechanism of PRL with the importance of two symmetrical tryptophan residues was proposed in detail to determine the conformational change of its receptor, which is essential for signal transduction. The better knowledge of PRLR structure and its protein-protein interaction can considerably contribute to a further understanding of PRLR signaling action and thereby help to develop some new PRLR signaling-based strategies for PRL-related diseases.

The influences of E22Q mutant on solvated 3Aß11-40 peptide: A REMD study.

The residue E22 plays a critical role in the aggregation process of Amyloid beta (Aß) peptides. The effect of E22Q mutant on the shapes of the solvated Aß11-40 trimer is clarified using a replica exchange molecular dynamics (REMD) simulation employing ∼20.6 µs of MD simulations with 48 disparate replicas. The increase of intramolecular polar contacts and salt bridge between the residue D23 to residues (24-29) was observed. The residual secondary structure of the mutated trimer is shifted in a similar way to the picture observed in previous investigations of F19W mutant. The free energy surface (FES) of the mutated E22Q system has a fewer number of minima in comparison with the wild-type trimer. The optimized shapes of the mutated E22Q form a significant increase in beta structure (47%) and serious decrease in coil content (46%) compared with the wild-type (of 36 and 56%, respectively). The binding affinity of constituting chains to the rest is of -43.7 ±â€¯6.5 kcal/mol, implying that the representative structure of E22Q is more stable than the wild-type one. Furthermore, the E22Q mutant increases the size of stable structures due to larger collision cross section (CCS) and solvent accessible area (SASA). The observed results may enhance the Aß inhibition throughout the contribution to the knowledge of the Aß oligomerization/aggregation.

Reaction Routes for Experimentally Observed Intermediates in the Prebiotic Formation of Nucleobases under High-Temperature Conditions.

The prebiotic synthesis of nucleobases is of particular interest, given the experimental evidence that indicated formation of the nucleobases under abiotic conditions on the Early Earth under high-temperature conditions. Biomolecules have been formed under meteoritic impact scenarios that lead to high temperature and the generation of high energy. Free radical pathways for the formation of biomolecules are appropriate under these conditions. Density functional theory computations were used to study the free radical routes for the formation of nucleobases at the UB3LYP/6-311G(d,p) level. We have found that both 5-aminoimidazole-4-carboxamide (AICA) and 5-(formylamino)imidazole-4-carboxamide (fAICA) are formed first from formamide then the nucleobases are formed. Calculated results show the radical reaction routes of AICA as a precursor for guanine. Both hypoxanthine and xanthine are formed from radical pathways of fAICA. In addition, generation of imino-AICA and imino-fAICA has been shown for the first time to be needed for the production of adenine, purine, and isoguanine. Formation of hypoxanthine and adenine/purine from fAICA and imino-fAICA, respectively, is consistent with experiments performed nearly seven decades ago.

Molecular details of spontaneous insertion and interaction of HCV non-structure 3 protease protein domain with PIP2-containing membrane.

Hepatitis C virus (HCV), known as the leading cause of liver cirrhosis, viral hepatitis, and hepatocellular carcinoma, has been affecting more than 150 million people globally. The HCV non-structure 3 (NS3) protease protein domain plays a key role in HCV replication and pathogenesis; and is currently a primary target for HCV antiviral therapy. Through unbiased molecular dynamics simulations which take advantage of the novel highly mobile membrane mimetic model, we constructed the membrane-bound state of the protein domain at the atomic level. Our results indicated that protease domain of HCV NS3 protein can spontaneously bind and penetrate to an endoplasmic reticulum complex membrane containing phosphatidylinositol 4,5-bisphosphate (PIP2). An amphipathic helix α0 and loop S1 show their anchoring role to keep the protein on the membrane surface. Proper orientation of the protein domain at membrane surface was identified through measuring tilt angles of two specific vectors, wherein residue R161 plays a crucial role in its final orientation. Remarkably, PIP2 molecules were observed to bind to three main sites of the protease domain via specific electrostatic contacts and hydrogen bonds. PIP2-interaction determines the protein orientation at the membrane while both hydrophobic interplay and PIP2-interaction can stabilize the NS3 - membrane complex. Simulated results provide us with a detailed characterization of insertion, orientation and PIP2-interaction of NS3 protease domain at membrane environment, thus enhancing our understanding of structural functions and mechanism for the association of HCV non-structure 3 protein with respect to ER membranes.

Replica exchange molecular dynamics study of the truncated amyloid beta (11-40) trimer in solution.

Amyloid beta (Aß) oligomers are neurotoxic compounds that destroy the brain of Alzheimer's disease patients. Recent studies indicated that the trimer is one of the most cytotoxic forms of low molecular weight Aß oligomers. As there was limited information about the structure of the Aß trimer, either by experiment or by computation, we determined in this work the structure of the 3Aß11-40 oligomer for the first time using the temperature replica exchange molecular dynamics simulations in the presence of an explicit solvent. More than 20.0 µs of MD simulations were performed. The probability of the ß-content and random coil structure of the solvated trimer amounts to 42 ± 6 and 49 ± 7% which is in good agreement with experiments. Intermolecular interactions in central hydrophobic cores play a key role in stabilizing the oligomer. Intermolecular polar contacts between D23 and residues 24-29 replace the salt bridge D23-K28 to secure the loop region. The hydrophilic region of the N-terminus is maintained by the intermolecular polar crossing contacts H13A-Q15B and H13B-Q15C. The difference in the free energy of binding between the constituting monomers and the others amounts to -36 ± 8 kcal mol-1. The collision cross section of the representative structures of the trimer was computed to be 1330 ± 47 Å2, which is in good agreement with previous experiments.

Comparative Study of Methanol Activation by Different Small Mixed Silicon Clusters Si2M with M = H, Li, Na, Cu, and Ag.

High-accuracy quantum chemical calculations were carried out to study the mechanisms and catalytic abilities of various mixed silicon species Si2M with M = H, Li, Na, Cu, and Ag toward the first step of methanol activation reaction. Standard heats of formation of these small triatomic Si clusters were determined. Potential-energy profiles were constructed using the coupled-cluster theory with extrapolation to complete basis set CCSD(T)/CBS, and CCSD(T)/aug-cc-pVTZ-PP for Si2Cu and Si2Ag. The most stable complexes generated by the interaction of methanol with the mixed clusters Si2M possess low-spin states and mainly stem from an M-O connection in preference to Si-O interaction, except for the Si2H case. In two competitive pathways including O-H and C-H bond breakings, the cleavage of the O-H bond in the presence of all clusters studied becomes predominant. Of the mixed clusters Si2M considered, the dissociation pathways of both O-H and C-H bonds with Si2Li turns out to have the lowest energy barriers. The most remarkable finding is the absence of the overall energy barrier for the O-H cleavage with the assistance of Si2Li. The breaking of O-H and C-H bonds with the assistance of Si2H, Si2Li, and Si2Na is kinetically preferred with respect to the Si2Cu and Si2Ag cases, apart from the case of Si2Na for O-H cleavage. In comparison with other transition-metal clusters with the same size, such as Cu3, Pt3, and PtAu2, the energy barriers for the O-H bond activation in the presence of small Si species, especially Si2H and Si2Li, are found to be lower. Consequently, these small mixed silicon clusters can be regarded as promising alternatives for the expensive metal-based catalysts currently used for methanol activation particularly and other dehydrogenation processes of organic compounds. The present study also suggests a further extensive search for other doped silicon clusters as efficient and more realistic gas-phase catalysts for important dehydrogenation processes in such a way that they can be experimentally prepared and implemented.

Structural assignment, and electronic and magnetic properties of lanthanide metal doped silicon heptamers Si7M0/- with M = Pr, Gd and Ho.

The ground state geometries of neutral and anionic lanthanide-metal-doped silicon clusters Si7M0/- with M = Pr, Gd and Ho were determined by quantum chemical (DFT) computations and the previous experimental photoelectron spectra were assigned. The hybrid B3LYP functional is suitable for predicting the ground electronic states of these Si clusters and reproducing well their photoelectron spectra. All the most stable isomers are substitutive derivatives of the bicapped octahedral pure Si80/- clusters. The bicapped octahedral Si7M is generated by substituting one Si atom on a plane of the D4h octahedron by one M atom. Replacement of a Si atom on the C2 axis of another bicapped octahedron by a lanthanide metal atom, where two capping Si atoms are situated in front of opposite triangular face on the side of the central square, gives rise to the anionic Si7M-. The limited participation of f-electrons of the lanthanide metal atoms on the valence electronic structure and thereby in the bonding of Si7M0/- induces high magnetic moments of the doped clusters. As a consequence, not only Si7M0/- but also SinLn0/- clusters can be regarded as suitable building blocks for assembling silicon-based cluster magnetic materials.

Fast and accurate determination of the relative binding affinities of small compounds to HIV-1 protease using non-equilibrium work.

The fast pulling ligand (FPL) out of binding cavity using non-equilibrium molecular dynamics (MD) simulations was demonstrated to be a rapid, accurate and low CPU demand method for the determination of the relative binding affinities of a large number of HIV-1 protease (PR) inhibitors. In this approach, the ligand is pulled out of the binding cavity of the protein using external harmonic forces, and the work of pulling force corresponds to the relative binding affinity of HIV-1 PR inhibitor. The correlation coefficient between the pulling work and the experimental binding free energy of R=-0.95 shows that FPL results are in good agreement with experiment. It is thus easier to rank the binding affinities of HIV-1 PR inhibitors, that have similar binding affinities because the mean error bar of pulling work amounts to δW=7%. The nature of binding is discovered using the FPL approach. © 2016 Wiley Periodicals, Inc.