Influence of soil amendment of different concentrations of amino acid water-soluble fertilizer on physiological characteristics, yield and quality of “Hangjiao No.2” Chili Pepper

Amino acids are well known as natural stimulators of plant growth and are widely used to promote crop yield and quality. Several studies have been conducted to investigate the effects of amino acid (s) as a foliar spray on a variety of plant species. However, the effects of soil amendment of different concentrations of amino acid water-soluble fertilizer on the physiological characteristics, yield, and quality of pepper remain unclear. Following this, three experimental sets of amino acid water-soluble fertilizer in the ratio 1.8: 2.7: 3.6 kg including control (CK) were conducted in Lintao county, Gansu province. The treatments were applied through furrow method at 6 weeks after planting. The results showed that physiological characteristics of the pepper plants, such as chlorophyll a (1.35 mg g−1), and b (0.67 mg g−1), total chlorophyll (2.02 mg g−1), carotenoid (0.63 mg g−1), ETR (26.25 µmol m−2s−1), Fv/Fm (0.75), Qp (0.92) contents of the leaves were increased by the 1.8 kg treatment while NPQ (71.37%) and root activity (2185.52 µg g−1 h−1) were improved by the 3.6 kg treatment compared to the control. Fertilization with 2.7 kg of amino acid water-soluble fertilizer also had a significant influence on fruit length (25.50 cm), and yield of pepper (37.92 t ha−1) while fruit diameter (24.51 mm), firmness (5.30 kg cm−2), fresh (48.10 g) and dry (4.71 g) weights were higher in the 1.8 kg treatment compared to the control. The lowest rate of fertilizer (1.8 kg) applied again resulted in a significant increase in soluble protein (79.79%), capsaicin (5.80 mg g−1), dihydrocapsaicin (1.08 mg g−1), vitamin C (72.33%) and the essential and non-essential amino acid contents of the pepper which ranged from (235.15 to 11.16 µg g−1) and (1,605.10 to 16.63 µg g−1) respectively, while soluble sugar (9.02%) was enhanced by 3.6 kg treatment compared to the control. The findings suggest that soil amendment with low concentration of amino acid water-soluble fertilizer (1.8 kg) could be successfully used to improve the physiological characteristics and fruit quality of peppers in vegetable production.

Kinetic instability of a chitosan – aspartic acid – water system as a method for obtaining nano- and microparticles

The specific electrical conductivity and dielectric constant of aqueous solutions of ionic aminopolysaccharide chitosan in L-aspartic acid were investigated. An increase of the mobility of charge carriers in these solutions was found in comparison with solutions of an individual acid. The evaluation of the kinetic stability revealed that the viscosity, electrical conductivity and dielectric constant of the chitosan – L-aspartic acid – water system decrease, while the pH value increases. It was shown that the time variation of physicochemical and electrochemical parameters is due to the effects of counterionic association with the transition of macromolecules to the ionomeric state and is accompanied by phase segregation of the polymer phase in the form of nano- and microparticles. The conducted studies carried out have shown the fundamental possibility of controlling the metastable state of this system in order to obtain nano- and microparticles.

Prediction of Partition Coefficients in SDS Micelles by DFT Calculations

A computational methodology using Density-Functional Theory (DFT) calculations was developed to determine the partition coefficient of a compound in a solution of Sodium Dodecyl Sulfate (SDS) micelles. Different sets of DFT calculations were used to predict the free energy of a set of 63 molecules in 15 different solvents with the purpose of identifying the solvents with similar physicochemical characteristics to the studied micelles. Experimental partition coefficients were obtained from Micellar Electrokinetic Chromatography (MEKC) measurements. The experimental partition coefficient of these molecules was compared with the predicted partition coefficient in heptane/water, cyclohexane/water, N-dodecane/water, pyridine/water, acetic acid/water, decan-1-ol/water, octanol/water, propan-2-ol/water, acetone/water, propan-1-ol/water, methanol/water, 1,2-ethane diol/water, dimethyl sulfoxide/water, formic acid/water, and diethyl sulphide/water systems. It is observed that the combination of pronan-1-ol/water solvent was the most appropriated to estimate the partition coefficient for SDS micelles. This approach allowed us to estimate the partition coefficient orders of magnitude faster than the classical molecular dynamics simulations. The DFT calculations were carried out with the well-known exchange correlation functional B3LYP and with the global hybrid functional M06-2X from the Minnesota functionals with 6-31++G ** basis set. The effect of solvation was considered by the continuum model based on density (SMD). The proposed workflow for the prediction rate of the participation coefficient unveiled the symmetric balance between the experimental data and the computational methods.