[Drug-resistant gene polymorphisms in Plasmodium falciparum isolated from Bioko Island, Equatorial Guinea in 2018 and 2019].

OBJECTIVE: To investigate the genetic polymorphisms of Plasmodium falciparum multidrug resistance protein 1 (PfMDR1), chloroquine resistance transporter (PfCRT) and Kelch 13 (PfK13) genes in Bioko Island, Equatorial Guinea, so as to provide insights into the development of the malaria control strategy in local areas. METHODS: A total of 85 peripheral blood samples were collected from patients with Plasmodium falciparum infections in Bioko Island, Equatorial Guinea in 2018 and 2019, and genomic DNA was extracted. The PfMDR1, PfCRT and PfK13 genes were amplified using a nested PCR assay. The amplification products were sequenced, and the gene sequences were aligned. RESULTS: There were no mutations associated with artemisinin resistance in PfK13 gene in Bioko Island, Equatorial Guinea, while drug-resistant mutations were detected in PfMDR1 and PfCRT genes, and the proportions of PfMDR1_N86Y, PfMDR1_Y184F and PfCRT_K76T mutations were 35.29% (30/85), 72.94% (62/85) and 24.71% (21/85), respectively. CONCLUSIONS: There are mutations in PfMDR1, PfCRT and PfK13 genes in P. falciparum isolates from Bioko Island, Equatorial Guinea.

Transparent Memory For Harsh Electronics.

As a new class of non-volatile memory, resistive random access memory (RRAM) offers not only superior electronic characteristics, but also advanced functionalities, such as transparency and radiation hardness. However, the environmental tolerance of RRAM is material-dependent, and therefore the materials used must be chosen carefully in order to avoid instabilities and performance degradation caused by the detrimental effects arising from environmental gases and ionizing radiation. In this work, we demonstrate that AlN-based RRAM displays excellent performance and environmental stability, with no significant degradation to the resistance ratio over a 100-cycle endurance test. Moreover, transparent RRAM (TRRAM) based on AlN also performs reliably under four different harsh environmental conditions and 2 MeV proton irradiation fluences, ranging from 1011 to 1015 cm-2. These findings not only provide a guideline for TRRAM design, but also demonstrate the promising applicability of AlN TRRAM for future transparent harsh electronics.

Deposition rule of yolk cholesterol in two different breeds of laying hens.

The objective of this study was to investigate the deposition rule of yolk cholesterol in Lushi Green-shelled and Silky Fowl layers. A total of 90 layers of each breed were selected at an age of 15 to 51 weeks. Productive performance was recorded on a weekly basis, whereas yolk cholesterol was determined at 4-week intervals from 21 to 51 weeks of age. The average yolk cholesterol content of Silky Fowl layers during the laying period was higher than that of Lushi Green-shelled layers (58.16 and 49.67%, P > 0.05). Yolk cholesterol content decreased at 21 to 31 weeks of the laying period, whereas a non-significant increasing trend was observed during 31 to 51 weeks of laying period. In conclusion, yolk cholesterol content is not only dependent on the age of hen but also the breed of layers.

A novel family of RNA tetraloop structure forms the recognition site for Saccharomyces cerevisiae RNase III.

RNases III are a family of double-stranded RNA (dsRNA) endoribonucleases involved in the processing and decay of a large number of cellular RNAs as well as in RNA interference. The dsRNA substrates of Saccharomyces cerevisiae RNase III (Rnt1p) are capped by tetraloops with the consensus sequence AGNN, which act as the primary docking site for the RNase. We have solved the solution structures of two RNA hairpins capped by AGNN tetraloops, AGAA and AGUU, using NMR spectroscopy. Both tetraloops have the same overall structure, in which the backbone turn occurs on the 3' side of the syn G residue in the loop, with the first A and G in a 5' stack and the last two residues in a 3' stack. A non-bridging phosphate oxygen and the universal G which are essential for Rnt1p binding are strongly exposed. The compared biochemical and structural analysis of various tetraloop sequences defines a novel family of RNA tetraloop fold with the consensus (U/A)GNN and implicates this conserved structure as the primary determinant for specific recognition of Rnt1p substrates.

Restraint-driven formation of alpha-helical coiled coils in molecular dynamics simulations.

The alpha-helical coiled coil motif is among the first characterized and widely found architecture of protein structures. We report here a fast and reliable approach of simulated annealing molecular dynamics (SA/MD) for predicting the three-dimensional structures of various alpha-helical coiled coils of heptad repeat. One key element of our simulation involves a geometric restraint requiring residues occupying the first and fourth positions of the heptad to orient to the angle of their respective statistical average derived from a survey of coiled-coil structures deposited in the Protein Data Bank. Another is the incorporation of subunit rotation and inversion operations for generating symmetrized protein assemblies during the dynamics simulations. The procedure is fully automated and can be applied to different oligomerization states of identical subunits, as well as both parallel and antiparallel arrangements. Despite simplicity, the formation of five coiled-coil prototype systems driven by the restraint-based SA/MD approach shows that the level of prediction accuracy achieved previously by more elaborate procedures can be retained. The present work thus provides validation of a simulation approach that can be employed to utilize a wide variety of knowledge-based geometric restraints for structural prediction of symmetrical or pseudo-symmetrical protein systems.

Estimates of relative binding free energies for HIV protease inhibitors using different levels of approximations.

Although the free energy perturbation approach is a rigorous method for estimating the relative binding free energy between an enzyme and its inhibitors, it is computationally expensive. This paper examines the accuracy at different levels of approximations, following the series expansion of free energy derived by Aqvist et al. Level-0 calculates only the enzyme-inhibitor interaction energy at the minimum energy configuration without solvent. In Level-0MD, the inhibitor configurations are sampled by molecular dynamics. These levels assume that the second- and higher order terms in the series expansion can be neglected and that the interaction energies in the bound and unbound states are equal. Level-1 does not assume equal interaction energies in the bound and unbound states. Level-1S includes the solvent contribution but both enzyme and inhibitor are fixed. In Level-1SMD, the inhibitor configurations are sampled by molecular dynamics. Level-2SMD retains the second-order term. We chose seven HIV-1 protease inhibitors for study: A77003, A76889, A76928, A78791, A74704, JG365 and MVT101. Level-0 and Level-0MD were found to give essentially the same relative interaction energies by using the AMBER force field, suggesting that fixing atomic positions may be a good approximation in some cases. However, as expected, Level-0 or Level-0MD gave poor predictions for the relative binding free energies between hydrophobic inhibitors (e.g. A77003) and more hydrophilic inhibitors (e.g. JG365). Level-1SMD produced a much better correlation between calculated and experimental results. Inclusion of the second-order term did not improve the accuracy.

Shaker pore structure as predicted by annealed atomic simulation using symmetry and novel geometric restraints.

Recent studies making use of channel-blocking peptides as molecular calipers have revealed the architecture of the pore-forming region of Shaker-type potassium channels. Here we show that the low-resolution, experimentally derived geometric information can be incorporated as restraints within the context of an annealed molecular dynamics simulation to predict an atomic structure for the channel pore which, by virtue of restraints, conforms to the experimental evidence. The simulation is reminiscent of the computational method employed by nuclear magnetic resonance (NMR) spectroscopists to resolve solution structures of biological macromolecules, but in lieu of restraints conventionally derived from NMR spectra, novel restraints are developed that include side-chain orientation of amino acid residues and assumed symmetry of protein subunits. The method presented here offers the possibility of expanding cooperation between simulation and experiment in developing structural models, especially for systems such as ion channels whose three-dimensional structures may not be amenable to determination by direct methods at the present time.

Elucidation of dose-effect relationships for different opiate effects using alfentanil in the spontaneously ventilating rat.

In addition to producing antinociception and mild sedation, opiates diminish spontaneous movement and produce muscle rigidity. Examination of the relationship between different opiate effects may lead to a better understanding of the mechanism and sites of action of opiate anesthesia. Previous studies have compared the dose-effect relationships for morphine and fentanyl between antinociception and loss of righting reflex. However, neither muscle rigidity nor lack of spontaneous movement (as measured by catalepsy) has been fully examined or directly compared with either antinociception or loss of righting reflex. This study, therefore, compared five clinically relevant opiate endpoints (antinociception, muscle rigidity, catalepsy, loss of righting reflex, and respiratory depression) using the mu-selective agonist alfentanil in the spontaneously ventilating rat. Rats were randomized to receive alfentanil (0-500 micrograms/kg) subcutaneously. For muscle rigidity, 59 rats had electromyographic activity measured with percutaneous hindlimb electrodes. After alfentanil injection, electromyographic data were recorded for 60 min. For antinociception and catalepsy, 49 rats were studied for 120 min after alfentanil. Catalepsy was measured from the time the rat's forelimbs were placed on a 10-cm-high bar until either limb was removed. Antinociception was studied by measuring tail-flick response to hot (55 degrees C) water. For righting reflex, 40 rats were studied for 120 min. Alfentanil-induced respiratory depression was assessed in 40 rats with indwelling tail arterial catheters. Alfentanil was administered after baseline arterial blood gas measurements, and then additional samples were obtained for 45 min. For each effect, data were converted into quantal responses and were then transformed to probit-log dose-response curves for analysis.(ABSTRACT TRUNCATED AT 250 WORDS)