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The Martini model, a coarse-grained forcefield for biomolecular simulations, has experienced a vast increase in popularity in the past decade. Its building-block approach balances computational efficiency with high chemical specificity, enabling the simulation of organic and inorganic molecules. The modeling of coarse-grained beads as Lennard-Jones particles poses challenges for the accurate reproduction of liquid-vapor interfacial properties, which are crucial in various applications, especially in the case of water. The latest version of the forcefield introduces refined interaction parameters for water beads, tackling the well-known artifact of Martini water freezing at room temperature. In addition, multiple sizes of water beads are available for simulating the solvation of small cavities, including the smallest pockets of proteins. This work focuses on studying the interfacial properties of Martini water, including surface tension and surface thickness. Employing the test-area method, we systematically compute the liquid-vapor surface tension across various combinations of water bead sizes and for temperatures from 300 to 350 K. These findings are of interest to the Martini community as they allow users to account for the low interfacial tension of Martini water by properly adjusting observables computed via coarse-grained simulations to allow for accurate matching against all-atom or experimental results. Surface tension data are also interpreted in terms of local enrichment of the various mixture components at the liquid-vapor interface by means of Gibbs' adsorption formalism. Finally, the critical scaling of the Martini surface tension with temperature is reported to be consistent with the critical exponent of the 3D Ising universality class., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

Polydimethylsiloxane (PDMS) is a popular silicon-based polymer with advanced applications in microfluidics and nanocomposites. The slow dynamics of polymer chains in such complex systems hinders molecular dynamics investigations based on all atom force fields. This limitation can be overcome by exploiting finely tuned coarse-grained (CG) models. This paper develops a transferable CG model of PDMS, compatible with the recent Martini 3 force field, using structural and thermodynamic properties as targets in the parametrization, including a vast set of experimental free energies of transfer. We validate the model transferability by reproducing the correct scaling laws for the PDMS gyration radius in the melt and good and bad solvents. We successfully test the model by reproducing the wetting behavior of water and acetonitrile on PDMS and the phase behavior of a PDMS-peptide triblock copolymer system. This work sets the stage for computational studies involving the interaction between PDMS and many synthetic and biological molecules modeled within the Martini framework.

Objective: Our study was aimed at comparing health behavior data collected from a Web-based self-administered questionnaire (Web SAQ) versus a paper-and-pencil self-administered questionnaire and assessing the feasibility of the application., Materials and Methods: One hundred and ninety (n = 190) pupils (ages 14-16 years) of senior high schools anonymously completed a questionnaire, with demographics and queries about lifestyle, alcohol, and tobacco use. For each class, the adolescents were randomly assigned to complete either the paper version of the questionnaire or the equivalent Web-based one, which used a customized platform developed for the purposes of this survey., Results: Females who filled out the Web SAQ required significantly less time and completed a significantly higher percentage of its items. Although the majority of questions on tobacco and alcohol did not differ significantly across the two administration modes, there were gender-related differences in some sensitive information. Male adolescents on the Web SAQ accounted higher per hour drink consumption (r = 0.27, p = 0.015) and more numerous episodes of inebriety (r = 0.26, p = 0.010), whereas females seemed to state a younger age of alcohol onset (r = 0.33, p = 0.002). Females were more likely to report being monthly smokers on the Web SAQ (odds ratio = 0.37). Adolescents felt significantly less observed and females referred being more independent while compiling the Web SAQ., Conclusions: The findings of the study suggest that differences in reporting of some behavior of adolescents when using a Web SAQ do exist, despite the small-to-medium effect sizes. Exploiting the Web requires further investigation for extensive comprehension of the reasons for such differences.