Binding of carmoisine,a food colorant,with hemoglobin: Spectroscopic and calorimetric studies

Interaction of the food colorant carmoisine with hemoglobin was studied using spectroscopic and calorimetric tools. The binding effected hypochromic changes in the Soret band of hemoglobin and induced remarkable quenching of the intrinsic fluorescence of hemoglobin. Synchronous fluorescence studies revealed that the polarity around the tryptophan residues of the protein was significantly increased in the presence of carmoisine whereas that around the tyrosine residues remained unchanged. Binding of carmoisine resulted in change of the secondary structure of hemoglobin reducing the helical composition to more than half the initial value. The binding was favored by large positive entropy changes and small but favorable enthalpy changes. The heat capacity change value and the occurrence of enthalpy–entropy compensation phenomena suggested the involvement of significant hydrophobic forces in the binding process. Detailed insights into the molecular interaction of carmoisine with hemoglobin are presented.     

稀土镧-芦丁配合物的合成与表征及其抑菌活性

为研究稀土芦丁配合物的结构和抑菌活性,以稀土金属镧（Ⅲ）的氯化物和芦丁为原料,在乙醇溶液中合成了镧-芦丁稀土配合物。以二甲基亚砜（DMSO）为溶剂,在200~400nm波长范围内对芦丁及配合物进行紫外光谱扫描,两个特征峰带分别发生了红移和蓝移。同时对配合物进行的傅立叶红外光谱分析显示,在614.88cm-1处出现的特征吸收峰表明芦丁与稀土镧(Ⅲ)以La-O键的形式结合成配合物,结果与紫外吸收光谱分析一致。同时研究了配合物在pH5~7时,浓度为2×10-5 mol?L-1~2×10-9 mol?L-1范围的荧光强度变化。抑菌活性实验表明,稀土镧-芦丁配合物的抑菌活性优于单独稀土镧（Ⅲ）离子和芦丁配体。将配合物用于纺织物的抗菌整理中,具有较强的抑菌活性。     

Preparation,characterization, and in vitro antitumor activity of folate conjugated chitosan coated EGCG nanoparticles

Folate conjugated chitosan coated EGCG nanoparticles (FCS-EGCG-NPs) were prepared using the ionic gelation method with folic acid modified carboxymethyl chitosan (FA-CMC) and chitosan hydrochloride as carriers of catechin EGCG. Characteristics of FCS-EGCG-NPs were determined using transmission electron microscopy (TEM) and fourier transform infrared spectroscopy (FTIR). Synthesized FCS-EGCG-NPs were spherical in shape with a mean diameter of 400 nm. The maximum encapsulation rate of nanoparticles loaded with EGCG was 75%. FTIR spectra suggested formation of an amide linkage between carboxyl groups of FA-CMC and the amine groups of chitosan hydrochloride. FCS-EGCG-NPs demonstrated sustained release of EGCG in buffer solutions of different pH values. The antitumor activity of FCS-EGCG-NPs towards different cancer cells was also investigated. FCS-EGCG-NPs had a greater tumor inhibition effect on cancer cells having a large expression of folic acid receptors on the surface than cancer cells with lesser expression.     

对氯苯氧乙酸-8-羟基喹啉稀土三元配合物的合成、表征及其抑菌活性

研究了以对氯苯氧乙酸、8-羟基喹啉为配体,以镱、铕为中心的稀土配合物。采用元素分析、摩尔电导、红外光谱、紫外光谱、荧光光谱、差热热重分析手段进行表征,并探讨了三元配合物对常见大肠杆菌和金黄色葡萄球菌、黑曲霉的抑菌活性。结果表明,合成的三元配合物的抑菌活性较配体均有提高。     

Spectroscopic studies on the interaction of sodium benzoate,a food preservative,with calf thymus DNA

The interaction between sodium benzoate (SB) and calf thymus DNA in simulated physiological buffer (pH 7.4) using acridine orange (AO) dye as a fluorescence probe, was investigated by UV–Vis absorption, fluorescence and circular dichroism (CD) spectroscopy along with DNA melting studies and viscosity measurements. An expanded UV–Vis spectral data matrix was resolved by multivariate curve resolution-alternating least squares (MCR−ALS) approach. The equilibrium concentration profiles and the pure spectra for SB, DNA and DNA–SB complex from the high overlapping composite response were simultaneously obtained. The results indicated that SB could bind to DNA, and hydrophobic interactions and hydrogen bonds played a vital role in the binding process. Moreover, SB was able to quench the fluorescence of DNA−AO complex through a static procedure. The quenching observed was indicative of an intercalative mode of interaction between SB and DNA, which was supported by melting studies, viscosity measurements and CD analysis.     

Stevioside and Stevia-sweetener in food: application, stability and interaction with food ingredients

The stability of the natural sweetener stevioside during different processing and storage conditions as well as the effects of its interaction with water-soluble vitamins, food relevant organic acids and other common low calorie sweeteners and its application in coffee and tea beverages were evaluated. Incubation of the solid sweetener stevioside at elevated temperatures for 1 h showed good stability up to 120°C, whilst at temperatures exceeding 140°C forced decomposition was noticed. In aqueous solutions stevioside is remarkable stable in a pH range 2–10 under thermal treatment up to 80°C, however, under strong acidic conditions (pH 1) a significant decrease in the stevioside concentration was detected. Up to 4 h incubation of stevioside with individual water-soluble vitamins in aqueous solution at 80°C showed no significant changes in regard to stevioside and the B-vitamins, whereas a protective effect of stevioside on the degradation of ascorbic acid was observed resulting in a significant delayed degradation rate. In the presence of other individual low calorie sweeteners practically no interaction was found at room temperature after 4 months incubation in aqueous media. Stability studies of stevioside in solutions of organic acids showed a tendency towards enhanced decomposition of the sweetener at lower pH values depending on the acidic medium. In a stevioside-sweetened coffee and tea beverage, practically, no significant chances neither in caffeine content nor in stevioside content could be noticed. Furthermore an overview of already performed studies in literature about the Stevia-sweetener stevioside and rebaudioside A is given.     

Anatase titanium dioxide loaded polylactide membranous films: preparation,characterization, and antibacterial activity assessment

In this study, the preparation method and characteristics of anatase titanium dioxide (TiO₂) nanoparticle-loaded polylactide (PLA) films and their antibacterial efficacy against Klebsiella pneumoniae (ATCC 4352) and Staphylococcus aureus (ATCC 6538) bacterium were studied. A series of PLA nanocomposites containing, respectively, 0, 1, and 5% (wt.) titanium dioxide (TiO₂) nanoparticles were prepared by melt intercalation method. The effect of TiO₂ nanoparticles on the thermal and mechanical characteristics of the films was determined. Thermal analysis showed that the glass transition temperature, crystallization temperature, melting temperature, and decomposition temperatures (Td_0.5 and Td_0.05) decreased with the filler content. The results obtained from tensile tests showed that TiO₂ nanoparticles reduced the mechanical properties and moduli of the PLA films. On the other hand, the water absorption properties of the nanocomposite films increased with the addition of nanoparticles and nanocomposite films exhibited bacteriostatic and limited bactericidal efficacy according to AATCC 147. Consequently, nanocomposite films may be good materials for medical applications due to their membranous properties.     

Starch-based nanoparticles: Stimuli responsiveness,toxicity, and interactions with food components

In recent years, starch-based nanoparticles have attracted great interest due to their small size, good biocompatibility, and environmental friendliness, as well as their potential applications in foods, drug delivery carriers, and biodegradable edible films. Compared with nonstarch polysaccharides, starch can be enzymatically hydrolyzed into glucose in vivo, so it can be used as an enzyme-responsive carrier. The recent research progress of starch-based nanoparticles, including starch nanoparticles, starch nanospheres, starch micelles, starch vesicles, starch nanogels, and starch nanofibers, are reviewed in this paper. The main focus is on their responsiveness, digestibility, toxicity, interactions with other components, and applications. Starch-based nanoparticles are nontoxic and responsive to pH, temperature, light, and other stimuli. It can interact with proteins, antioxidants, and lipids through electrostatic interactions and hydrogen bonding interactions. Starch-based nanoparticles have a wide range of applications, including enhancing the mechanical properties of films and gels, stabilizing emulsions, as a fluorescent indicator, a catalyst, and a nanocarrier to control the release of active ingredients and drugs.     

Entomotoxic efficacy of aluminium oxide,titanium dioxide and zinc oxide nanoparticles against Sitophilus oryzae (L.): A comparative analysis

The development of resistance in both stored grain and field insect pests to conventional insecticides, coupled with increased consumer awareness of the consequences of their residual toxicity in food crops and environmental contamination have led agro-chemical researchers to reappraise the use of inert dusts as alternative insecticide. Diatomaceous Earth or DE became popular as an alternative insecticide in last two decades for its low mammalian toxicity and physical mode of action. But due to several limitations of DE many researchers are trying to explore the possibility of using nanoparticles as potential insecticide. In this study, a comparison on entomotoxic efficacy of different oxide nanoparticles like aluminium oxide, titanium dioxide and zinc oxide was evaluated on Sitophilus oryzae. Though more than 90% S. oryzae died after 4 days of nano aluminium oxide treatment at 1 g kg⁻¹ dosage, nano zinc oxide and titanium dioxide treatment could attain this efficacy at 2 g kg⁻¹ after 14 days. Even then use of nano zinc oxide and titanium dioxide in agriculture sector is preferred to nano aluminium oxide as the latter nanoparticle has adverse effects on plant growth. Moreover due to the antimicrobial property of nano zinc oxide and titanium dioxide have antimicrobial property, they will not only protect the agricultural produce from insect pests, but also from microbial infection.     

Stevioside and Stevia-sweetener in food: application, stability and interaction with food ingredients

The stability of the natural sweetener stevioside during different processing and storage conditions as well as the effects of its interaction with water-soluble vitamins, food relevant organic acids and other common low calorie sweeteners and its application in coffee and tea beverages were evaluated. Incubation of the solid sweetener stevioside at elevated temperatures for 1 h showed good stability up to 120°C, whilst at temperatures exceeding 140°C forced decomposition was noticed. In aqueous solutions stevioside is remarkable stable in a pH range 2–10 under thermal treatment up to 80°C, however, under strong acidic conditions (pH 1) a significant decrease in the stevioside concentration was detected. Up to 4 h incubation of stevioside with individual water-soluble vitamins in aqueous solution at 80°C showed no significant changes in regard to stevioside and the B-vitamins, whereas a protective effect of stevioside on the degradation of ascorbic acid was observed resulting in a significant delayed degradation rate. In the presence of other individual low calorie sweeteners practically no interaction was found at room temperature after 4 months incubation in aqueous media. Stability studies of stevioside in solutions of organic acids showed a tendency towards enhanced decomposition of the sweetener at lower pH values depending on the acidic medium. In a stevioside-sweetened coffee and tea beverage, practically, no significant chances neither in caffeine content nor in stevioside content could be noticed. Furthermore an overview of already performed studies in literature about the Stevia-sweetener stevioside and rebaudioside A is given.     

Hydroformylation of 1-hexene in supercritical carbon dioxide: characterization, activity, and regioselectivity studies

The hydroformylation of alkenes is a major commercial process used for the production of oxygenated organic compounds. When the hydroformylation reaction is performed using a homogeneous catalyst, an organic or aqueous solvent is employed, and a significant effort must be expended to recover the catalyst so it can be recycled. Development of a selective heterogeneous catalyst would allow simplification of the process design in an integrated system that minimizes waste generation. Recent studies have shown that supercritical carbon dioxide (scCO2) as a reaction solvent offers optimal environmental performance and presents advantages for ease of product separation. In particular, we have considered the conversion of 1-hexene to heptanal using rhodium- and platinum-phosphine catalysts tethered to supports insoluble in scCO2 to demonstrate the advantages and to understand the limitations of a solid-catalyzed process. One of the historical limitations of supported catalysts is the inability to control product regioselectivity. To address this concern, we have developed tethered catalysts with phosphinated silica and controlled pore size MCM-41 and MCM-20 supports that provide improved regioselectivity and conversion relative to their nonporous equivalents. Platinum catalysts supported on MCM-type supports were the most regioselective whereas the analogous rhodium catalysts were the most active for hydroformylation of 1-hexene in scCO2.     

Silver/chitosan-based Janus particles: Synthesis,characterization, and assessment of antimicrobial activity in vivo and vitro

Janus particles containing chitosan and silver were synthesized in an eco-friendly manner and were confirmed using transmission electron microscopy. Based on the data of the antimicrobial activity assessment, this material exhibited a higher antimicrobial activity than virgin chitosan with long–lasting antibacterial effectiveness against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Salmonella choleraesuis bacteria, as well as Botrytis cinerea fungi. The results showed that the Janus polymer could completely suppress the growth and germination of B. cinerea at a concentration of 0.02 mg/mL in vitro and in vivo. This Janus polymer is an advanced functional material that combines the suitable properties of both components and could be an alternative new antimicrobial agent due to its unique chemical properties and pronounced antimicrobial activity. This material is a potential candidate for use in the food industry to prevent microbial contamination and to inhibit the growth of microorganisms, enhancing product quality and, extend shelf-life of fresh and processed agri-food products.     

A novel bacteriocin against Staphylococcus aureus from Lactobacillus paracasei isolated from Yunnan traditional fermented yogurt: Purification,antibacterial characterization,and antibiofilm activity

Staphylococcus aureus and its biofilm have emerged as a significant threat to the safety of dairy products. In recent years, lactic acid bacteria (LAB) bacteriocins have been widely acknowledged as the potential natural antibacterial substance in food biopreservation due to their excellent antibacterial effects. However, few LAB bacteriocins with antibacterial and antibiofilm activity against S. aureus have been reported in dairy products. In the present study, a novel bacteriocin LSX01 of Lactobacillus paracasei LS-6 isolated from a traditional fermented yogurt produced in Yunnan, China, was purified and characterized extensively. The LSX01 possessed a molecular weight of 967.49 Da and an AA sequence of LDQAGISYT. The minimum inhibitory concentration of LSX01 against S. aureus_45 was 16.90 μg/mL, which was close to or lower than the previously reported bacteriocins. The LSX01 exhibited an extensive antimicrobial spectrum against both gram-positive and gram-negative bacteria. Moreover, LSX01 exhibited excellent tolerance to heat and acid-base treatments, and sensitivity to the proteolytic enzymes, such as pepsin and proteinase K. Furthermore, the treatment of S. aureus_45 planktonic cells with LSX01 significantly reduced their metabolic activity and disrupted the cell membrane integrity. Scan electron microscopy results demonstrated that LSX01 induced cytoplasmic content leakage and cell deformation. Additionally, biofilm formation of S. aureus_45 was also significantly inhibited by LSX01. Overall, the results suggested that the novel LAB bacteriocin LSX01 possessed antibacterial activity and antibiofilm activity against S. aureus and, hence, could have potential for improving safety of dairy products.     

Interaction of fullerene (C60) nanoparticles with humic acid and alginate coated silica surfaces: measurements, mechanisms, and environmental implications

The deposition kinetics of fullerene (C60) nanoparticles onto bare silica surfaces and surfaces precoated with humic acid and alginate are investigated over a range of monovalent (NaCI) and divalent (CaCl2) salt concentrations using a quartz crystal microbalance. Because simultaneous aggregation of the fullerene nanoparticles occurs, especially at higher electrolyte concentrations, we normalize the observed deposition rates by the corresponding favorable (transport-limited) deposition rates to obtain the attachment efficiencies, alpha. The deposition kinetics of fullerene nanoparticles onto bare silica surfaces are shown to be controlled by electrostatic interactions and van der Waals attraction, consistent with the classical particle deposition behavior where both favorable and unfavorable deposition regimes are observed. The presence of dissolved humic acid and alginate in solution leads to significantly slower deposition kinetics due to steric repulsion. Precoating the silica surfaces with humic acid and alginate exerts similar steric stabilization in the presence of NaCl. In the presence of CaCl2, the deposition kinetics of fullerene nanoparticles onto both humic acid- and alginate-coated surfaces are relatively high, even at relatively low (0.3 mM) calcium concentration. This behavior is attributed to the macromolecules undergoing complex formation with calcium ions, which reduces the charge and steric influences of the adsorbed macromolecular layers.