Conformational Flexibilities and Solvation Properties of Insulin in Aromatic Amino Acid Solutions: A Molecular Dynamics Study Using CHARMM Drude Polarizable Model

Aromatic amino acids (AAA) play a crucial role in the structure and function of proteins. A higher level of AAA causes several diseases, controls insulin levels. In this work, we carried out atomistic molecular dynamics simulations by using CHARMM Drude polarizable force field to investigate the conformational properties of insulin monomer in 2M phe, tyr, trp solutions as well as in pure aqueous solution to compare the relative changes of protein conformations, its solvation properties and the interactions of the free AAA with insulin. Although insulin’s native folded form was intact in all the solutions within the simulation length scale, we observed that the protein is a little more flexible and less compact in phe solution than in tyr/trp solutions. The free AAAs identified to self-aggregate around the protein surface and form clusters of different sizes. They interacted with insulin, significantly through cation/anion–[Formula: see text] and [Formula: see text]–[Formula: see text] stacking, and partly through hydrogen bonded interactions. Among the three, trp was prone to interact through cation–[Formula: see text] interactions while phe and tyr interacted through [Formula: see text]–[Formula: see text] stacking with insulin. Despite a significant number of free AAA molecules in the solvation shell, insulin was observed to be sufficiently hydrated and formed hydrogen bonds with water. Some of our findings agreed with the available experimental results that establish the reliability of the chosen force field. Our findings would interpret the interactions between the free AAA and insulin in solution, helpful to recognize the microscopic details of AAA governed biological processes in living organisms.

The influence of aromatic amino acids on the chemical composition of mint plants genus (Mentha L.)

The aromatic amino acids, tryptophan, phenylalanine and tyrosine, are not only components of proteins, but also precursors of many compounds in plants that have a significant impact on their growth, development, reproduction and protective function against various abiotic and biotic factors. With the growing demand for plant-derived chemical compounds, much in vitro and in vivo research is being conducted to intensify the synthesis of these compounds or to change their qualitative composition in plants. The aim of the research was to evaluate the influence of aromatic amino acids on the chemical composition of different varieties of Mentha L. plants. The field experiment was conducted at Aleksandras Stulginskis University (ASU) in 2017–2019, since 2019 at the Vytautas Magnus University Agricultural Academy Experimental Station, which is located in Ringaudai Eldership, Kaunas District (coordinates 54 ° 53′ 08.9″ N, 23° 50′ 08.02″ E). The effect of different concentrations of amino acid solutions on the chemical composition of mints depended on the mint variety. Spraying with all amino acids solutions significantly increased the dry matter, crude fiber and crude ash content in M. spicata ‘Crispa’ mints while a positive effect of amino acids solutions on the protein content was found only in M. piperita ‘Granada’ mints sprayed only with 200 mg l–1 tyrosine solution, where the amount of protein increased significantly by 1.41-fold compared to that of non-sprayed plants. The intensity of the synthesis of photosynthetic pigments depended on the amino acid solutions used and the variety of mint. There were both inhibitory and stimulatory effects.

Vitamins and trace elements as essential components of parenteral nutrition

In certain clinical situations, the usual food intake is impossible, insufficient or contraindicated, which causes nutritional deficiency with a deficiency of all macro- and micronutrients, and worsens the prognosis and treatment results. In such cases, parenteral nutrition (PN) is used to compensate for the deficiency of nutrients. Complex parenteral nutrition, along with macronutrients (amino acid solutions, fat emulsions and carbohydrates), includes solutions of vitamins (multivitamins, MVC) and trace elements (trace elements complexes, TEC). The aim of this work was to review the results of studies over the past 30 years on the clinical use of MVC and TEC for injections within the framework of the international ASPEN and ESPEN recommendations for the prevention and treatment of a number of diseases and pathological conditions accompanied by vitamin and trace elements deficiency, including full or partial PN. In accordance with international recommendations based on the results of most randomized clinical trials, the use of MVC and TEC allows preventing and eliminating vitamin and trace elements deficiency during long-term complete and/or partial PN, accelerating the recovery process of patients in critical conditions, and reducing the time spent in the ICU and in the clinic as a whole, to reduce the number of complications and mortality.

Temperature Dependence of Volumetric and Viscometric Studies on SDS in Amino Acid Solutions

The temperature dependence studies on the binary and ternary system are very few. The densities of sodium dodecyl sulphate (SDS), L-arginine, 2-amino butyric acid in water and SDS mixed with L-arginine and 2-amino butyric acid solutions have been measured precisely at five equidistant temperatures ranging from 293.15K to 313.15K at an interval of 5K. The variety of different thermo- dynamics properties of SDS were observed in the low concentration region. The density of all the studied system was found to increase with the increase of molar concentration of the solution and decrease with the increase of temperature. SDS acts as structure breaker for both regions in aqueous L-arginine and 2-amino butyric acid solvent system at studied temperature.