Insights into the activity and specificity of Trypanosoma cruzi trans-sialidase from molecular dynamics simulations.

Trypanosoma cruzitrans-sialidase (TcTS), which catalyzes the transfer or hydrolysis of terminal sialic acid residues, is crucial to the development and proliferation of the T. cruzi parasite and thus has emerged as a potential drug target for the treatment of Chagas disease. We here probe the origin of the observed preference for the transfer reaction over hydrolysis where the substrate for TcTS is the natural sialyl donor (represented in this work by sialyllactose). Thus, acceptor lactose preferentially attacks the sialyl-enyzme intermediate rather than water. We compare this with the weaker preference for such transfer shown by a synthetic donor substrate, 4-methylumbelliferyl α-d-acetylneuraminide. For this reason, we conducted molecular dynamics simulations of TcTS following its sialylation by the substrate to examine the behavior of the asialyl leaving group by the protein. These simulations indicate that, where lactose is released, this leaving group samples well-defined interactions in the acceptor site, some of which are mediated by localized water molecules; also, the extent of the opening of the acceptor site to solvent is reduced as compared with those of unliganded forms of TcTS. However, where there is release of 4-methylumbelliferone, this leaving group explores a range of transient poses; surrounding active site water is also more disordered. The acceptor site explores more open conformations, similar to the case in which the 4-methylumbelliferone is absent. Thus, the predicted solvent accessibility of sialylated TcTS is increased when 4-methylumbelliferyl α-d-acetylneuraminide is the substrate compared to sialyllactose; this in turn is likely to contribute to a greater propensity for hydrolysis of the covalent intermediate. These computational simulations, which suggest that protein flexibility has a role in the transferase/sialidase activity of TcTS, have the potential to aid in the design of anti-Chagas inhibitors effective against this neglected tropical disease.

Developing the Accuracy of Vital Sign Measurements Using the Lifelight Software Application in Comparison to Standard of Care Methods: Observational Study Protocol.

BACKGROUND: Vital sign measurements are an integral component of clinical care, but current challenges with the accuracy and timeliness of patient observations can impact appropriate clinical decision making. Advanced technologies using techniques such as photoplethysmography have the potential to automate noncontact physiological monitoring and recording, improving the quality and accessibility of this essential clinical information. OBJECTIVE: In this study, we aim to develop the algorithm used in the Lifelight software application and improve the accuracy of its estimated heart rate, respiratory rate, oxygen saturation, and blood pressure measurements. METHODS: This preliminary study will compare measurements predicted by the Lifelight software with standard of care measurements for an estimated population sample of 2000 inpatients, outpatients, and healthy people attending a large acute hospital. Both training datasets and validation datasets will be analyzed to assess the degree of correspondence between the vital sign measurements predicted by the Lifelight software and the direct physiological measurements taken using standard of care methods. Subgroup analyses will explore how the performance of the algorithm varies with particular patient characteristics, including age, sex, health condition, and medication. RESULTS: Recruitment of participants to this study began in July 2018, and data collection will continue for a planned study period of 12 months. CONCLUSIONS: Digital health technology is a rapidly evolving area for health and social care. Following this initial exploratory study to develop and refine the Lifelight software application, subsequent work will evaluate its performance across a range of health characteristics, and extended validation trials will support its pathway to registration as a medical device. Innovations in health technology such as this may provide valuable opportunities for increasing the efficiency and accessibility of vital sign measurements and improve health care services on a large scale across multiple health and care settings. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/14326.

Tryptophan as a molecular shovel in the glycosyl transfer activity of Trypanosoma cruzi trans-sialidase.

Molecular dynamics investigations into active site plasticity of Trypanosoma cruzi trans-sialidase, a protein implicated in Chagas disease, suggest that movement of the Trp(312) loop plays an important role in the enzyme's sialic acid transfer mechanism. The observed Trp(312) flexibility equates to a molecular shovel action, which leads to the expulsion of the donor aglycone leaving group from the catalytic site. These computational simulations provide detailed structural insights into sialyl transfer by the trans-sialidase and may aid the design of inhibitors effective against this neglected tropical disease.

Mindfulness-Based Interventions in Recurrent Ovarian Cancer: A Mixed-Methods Feasibility Study.

A recurrence of cancer is a traumatic and stressful experience, and a number of approaches have been proposed to manage or treat the associated psychological distress. Meditative techniques such as mindfulness may be able to improve an individual's ability to cope with stressful life events such as cancer diagnosis or treatment. This single-arm mixed-methods study primarily aimed to determine the feasibility of using a mindfulness-based intervention in managing psychosocial distress in recurrent ovarian cancer. Twenty-eight participants took part in a mindfulness-based program, involving six group sessions, each lasting 1.5 hours and delivered at weekly intervals. The study found that the mindfulness-based intervention was acceptable to women with recurrent ovarian cancer and feasible to deliver within a standard cancer care pathway in a UK hospital setting. The results suggested a positive impact on symptoms of depression and anxiety, but further study is needed to explore the effectiveness of the intervention.

Molecular dynamics study of chemically engineered green fluorescent protein mutants: comparison of intramolecular fluorescence resonance energy transfer rate.

Because of its unusual spectroscopic properties, green fluorescent protein (GFP) has become a useful tool in molecular genetics, biochemistry and cell biology. Here, we computationally characterize the behavior of two GFP constructs, designed as bioprobes for enzymatic triggering using intramolecular fluorescence resonance energy transfer (FRET). These constructs differ in the location of an intramolecular FRET partner, an attached chemical chromophore (either near an N-terminal or C-terminal site). We apply the temperature replica exchange molecular dynamics method to the two flexible constructs in conjunction with a generalized Born implicit solvent model. The calculated rate of FRET was derived from the interchromophore distance, R, and orientational factor, kappa(2). In agreement with experiment, the construct with the C-terminally attached dye was predicted to have higher energy transfer rate than observed for the N-terminal construct. The molecular basis for this observation is discussed. In addition, we find that the orientational factor, kappa(2), deviates from the commonly assumed value, the implications of which are also considered.

Molecular probes: insights into design and analysis from computational and physical chemistry.

The application of new molecular diagnostics to probe cellular process in vivo is leading to a greater understanding of molecular cytology at a sub-nanoscale level and is opening the way to individualized medicines. We review here three distinct fluorescence-based molecular probes, HyBeacons, split-probe exciplexes and GFP (green fluorescent protein)-based FRET (fluorescence resonance energy transfer) systems. Through this, we highlight the insights into the mechanism and design that a combined computational and experimental approach can yield.