Estimation of Uptake of Humic Substances from Different Sources by Escherichia coli Cells under Optimum and Salt Stress Conditions by Use of Tritium-Labeled Humic Materials▿

The primary goal of this paper is to demonstrate potential strengths of the use of tritium-labeled humic substances (HS) to quantify their interaction with living cells under various conditions. A novel approach was taken to study the interaction between a model microorganism and the labeled humic material. The bacterium Escherichia coli was used as a model microorganism. Salt stress was used to study interactions of HS with living cells under nonoptimum conditions. Six tritium-labeled samples of HS originating from coal, peat, and soil were examined. To quantify their interaction with E. coli cells, bioconcentration factors (BCF) were calculated and the amount of HS that penetrated into the cell interior was determined, and the liquid scintillation counting technique was used as well. The BCF values under optimum conditions varied from 0.9 to 13.1 liters kg−1 of cell biomass, whereas under salt stress conditions the range of corresponding values increased substantially and accounted for 0.2 to 130 liters kg−1. The measured amounts of HS that penetrated into the cells were 23 to 167 mg and 25 to 465 mg HS per kg of cell biomass under optimum and salt stress conditions, respectively. This finding indicated increased penetration of HS into E. coli cells under salt stress

Structural peculiarities of lysozyme – PLURONIC complexes at the aqueous-air and liquid-liquid interfaces and in the bulk of aqueous solution

Interaction between proteins and synthetic polymers that represent a perspective potential in drug delivery or/and already used in medicine plays a key role in biological functioning of both molecules along with a system as a whole. In present study association between hen egg white lysozyme and Pluronic triblock-copolymers (L121, P123 and F127) in the bulk of the solution as well as at the aqueous-air and liquid-liquid interfaces was analyzed by means of spectroscopic and radiochemical assay. In protein-Pluronic complexes lysozyme keeps the secondary structure (CD and SAXS data results), while fluorescence and UV-analysis indicates changes in the local surrounding of fluorophoric amino acid residues. Radiochemical assay in combination with molecular docking reveals the formation of the complexes, in which proline residues turned to the interface between water and hydrophobic medium

Higher-Order Soliton Generation in Hybrid Mode-Locked Thulium-Doped Fiber Ring Laser

Abstract-A thulium-doped all-fiber laser passively modelocked by the co-action of nonlinear polarization evolution and single-walled carbon nanotubes operating at 1860-1980 nm wavelength band is demonstrated. Pumped with the single-mode laser diode at 1.55 μm laser generates near 500-fs soliton pulses at repetition rate ranging from 6.3 to 72.5 MHz in single-pulse operation regime. Having 3-m long cavity average output power reached 300 mW, giving the peak power of 4.88 kW and the pulse energy of 2.93 nJ with slope efficiency higher than 30%. At a 21.6-m long ring cavity average output power of 117 mW is obtained, corresponding to the pulse energy up to 10.87 nJ and a pulse peak power of 21.7 kW, leading to the higher-order soliton generation. Index Terms-Carbon nanotubes, fiber lasers, laser mode locking, optical pulse shaping