Lithuanian Journal of Physics

Title

2026-04-29T15:19:12+03:00

2026-04-29T15:20:52+03:00

Introduction

2026-05-04T14:35:26+03:00

Conformational analysis of small ethanol clusters trapped in a low-temperature argon matrix

2026-04-30T15:18:32+03:00

This work presents a conformational analysis of ethanol molecules and their clusters isolated in a low-temperature argon matrix using FTIR spectroscopy and quantum-chemical calculations. Optimal geometry, energy parameters and vibrational frequencies for trans and gauche conformations of ethanol, as well as for various possible combinations of conformers in dimers, trimers and tetramers, were calculated. Temperature-dependent FTIR spectra reveal distinct bands corresponding to the O–H stretching vibrations of both conformers. As the matrix temperature increases from 20 to 50 K, ethanol monomers progressively form hydrogen-bonded clusters. Quantum-chemical modelling confirms the presence of all theoretically predicted cluster configurations in the matrix at temperatures about 40 K.

Thermophilic proteins – exploring thermal stability of FN3 domain from Thermoanaerobacter tengcongensis based on in silico experiments

2026-04-30T15:18:20+03:00

Extremophilic proteins exhibit a remarkable stability under extreme conditions (e.g. thermophilic systems are stable at elevated temperatures), offering insights into molecular adaptations and early life on Earth. Currently, thermophilic organisms are widely investigated, and they constitute a challenge for new industrial and pharmaceutical applications. Examples of studies on extremophiles, including thermophiles, reach as far as space exploration experiments. The Fibronectin Type 3 (FN3) domain, a conserved structural motif, plays key roles in protein interactions and stability. This study investigates the thermal stability of the FN3 domain from the thermophilic bacterium Thermoanaerobacter tengcongensis. The domains of the wild type and its triple mutant FN3 were simulated (Protein Data Bank ids: 7jgt and 7jgu, respectively), with a wild-type human analogue (Protein Data Bank id: 5kf4) as a control, using molecular dynamics (MD) with classical force field. The simulations were performed at 300, 350 and 400 K temperatures to show their impact on the molecular properties. Structural parameters were analyzed, including root mean square deviation (RMSD), root mean square fluctuations (RMSF), solvent accessible surface area (SASA), secondary structure assignment and hydrogen bond networks. The obtained results reveal that the thermophilic bacterial variants of the FN3 domain exhibit lower structural fluctuations, particularly in residues 10–20 and 50–60, compared to the human analogue. The bacterial FN3 mutant exhibited reduced stability compared to the wild type, highlighting the importance of hydrogen bonding network in ensuring thermal stability. These findings enhance our understanding of the molecular mechanisms underlying the stability and adaptation of extremophilic proteins to high temperatures.

Could carotenoids advance the sensing properties of KL1421 luminophore? Theoretical study

2026-04-30T15:18:08+03:00

This computational chemistry research was performed using Becke’s three-parameter hybrid functional approach with the non-local correlation provided by Lee, Yang and Parr, and the cc-pVTZ basis set. The geometry, its change, and the charge redistribution in KL1421 when the molecule interacts with carotenoids and/or sensed molecules such as NH3 and acetic acid were studied. The orbital diagrams were used to illustrate the excitations and their variations resulting from the formation of the above complexes. The increase in molar absorptivity is observed in compounds with carotenoids, leading to a higher absorbance of KL1421. The latter allows us to conclude that a large amount of energy could be emitted, or the emission becomes longer. Additionally, the analysis of the oscillator strengths reveals that the strong interaction among species in KL1421 could facilitate radiation emission. We concluded that carotenoids could improve the sensing properties of the KL1421 luminophore.

Investigation of visceral adipose tissue (VAT) surface using microscopic methods

2026-04-30T15:19:31+03:00

In this study, optical microscopy (OM) and scanning electron microscopy (SEM) were used to characterize visceral adipose tissue (VAT) samples collected from volunteer patients with obesity. The focus was on examining the relationship between the morphological features of VAT samples from individuals with and without metabolic diseases. The microscopic images provided insights into the key morphological characteristics of VAT layers in obese individuals. The OM images of adipose tissue from visceral layers of various obese patients with metabolic diseases revealed the formation of lipid droplets of varying sizes and oval shapes. The SEM micrographs of VAT samples from obese patients with metabolic diseases showed the presence of single circular formations, voids, and other distinct morphological features. The OM and SEM findings could potentially be used to assess metabolic symptoms and predict various diseases in patients with obesity.

Relaxation dynamics of guanosine 5’-monophosphate with Na+ and K+ in aqueous solutions investigated by broadband dielectric spectroscopy

2026-04-30T15:29:03+03:00

To gain insights into nucleotide–monovalent ions interaction, the dynamics of counterions (sodium and potassium) with guanosine 5'-monophosphate (5'-GMP) were studied in an aqueous solution via broadband dielectric spectroscopy measurements. Complex reflection coefficients of aqueous Na-GMP and K-GMP solutions are measured in the frequency domain at room temperature. Complex specific resistance spectra are analyzed at various mononucleotide concentrations. One dispersion region located at 100 MHz was observed. It is interpreted as being caused by DNA counterion fluctuations. It largely depends on the GMP concentration in the solution.

Experimental (Raman and IR) and computational (DFT) studies of the cyclohexyltrifluorosilane

2026-04-30T15:17:44+03:00

This study presents an experimental (Raman and IR spectroscopy) and computational (DFT) investigation of cyclohexyltrifluorosilane to identify its stable conformers and assign its experimental vibrational spectral bands. Computational analysis confirmed the existence of two stable chair conformers: chair equatorial (most stable) and chair axial. The potential energy difference between these conformers was found to be 6.3 kJ/mol, and the interconversion barrier was determined to be too high to overcome it at matrix experiments conditions. To provide a complete assignment of the compound’s vibrational spectral bands, experimental data from ATR-FTIR, Raman, and matrix isolation IR spectroscopy were used in conjunction with DFT calculations. The experimental results confirm the existence of only one conformer in the chair equatorial configuration.

On the proton spin diffusion in powdered fumaric acid

2026-05-06T13:50:21+03:00

Spin diffusion is a well-established phenomenon in solid-state NMR, providing means to probe the molecular structure and transfer magnetization over extended intramolecular distances. Recently, we demonstrated that highly polarized 13C nuclei in 1-13C-fumaric acid can relay magnetization across crystallite boundaries to other 13C-labelled powders. To explore the possibility of using the abundant 1H network, in the present study, dry powdered fumaric acid was examined using conventional solid-state NMR techniques characterizing local order, relaxation and dynamical properties. The results reveal that, although 1H spin diffusion is intrinsically slow, both the diffusion rate and polarization lifetime increase with temperature. This offers new practical insights into the proton-mediated spin diffusion and may aid in designing more eﬀicient polarization-relay strategies.