Interaction of porphyrins with concanavalin a and pea lectin

Currently porphyrins are used as photosensitizers in photodynamic therapy for the treatment of cancer. However, this approach suffers due to the inability of many porphyrin-based drugs to accumulate preferentially in tumours. In view of this, we considered if the carbohydrate-binding proteins, lectins, which preferentially recognize malignant cells, could be used for the targeting of porphyrins to tumour cells. In the present study, we have investigated the interaction of a free base porphyrin, meso-tetrasulphonatophenylporphyrin and the corresponding metal derivative, meso-zinc-tetrasulphonatophenylporphyrin with two legume lectins, concanavalin A and pea (Pisum sativum) lectin. Each lectin subunit was found to bind one porphyrin molecule and the association constant, Ka, estimated from absorption and fluorescence titrations at room temperature (28 +/- 1 degree centigrade) was in the range of 1.2 X 10 to the power of 4 M to the power of -1 to 6.3 X 10 to the power of 4 M to the power of -1. Both free lectin and lectin saturated with the specific saccharide were found to bind the porphyrin with comparable binding strength, indicating that porphyrin binding takes place at a site different from the sugar-binding site. These results indicate that lectins may potentially serve as drug-delivery agents for porphyrin sensitizers in photodynamic therapy

Liquid organic hydrogen carriers:Process design and economic analysis for manufacturing N-ethylcarbazole

This paper revisits the economics of manufacturing N-ethylcarbazole (NEC), a strong candidate for large-scale liquid organic hydrogen carrier (LOHC) supply chains, because of its high H2 storage capacity (6 wt%), selective hydrogenation and dehydrogenation reactions, and favorable reaction enthalpy and reaction temperatures compared to other LOHC systems. Two different process routes for producing NEC from industrial chemicals are selected out of 10 possible options: one using aniline and the other using cyclohexanone and nitrobenzene as feedstock. The required capital and operational costs are estimated to determine a NEC break-even cost for a capacity of 225 ktpa. NEC break-even costs of $3.0 and$2.6 per kg LOHC are found for the routes. This is significantly less than the $40/kg cost that has generally been reported in literature for NEC, thus improving the economic viability of using NEC as LOHC. The total fixed capital costs are estimated to be$200 MM and $250 MM. Furthermore, the prices of the feedstock show the largest influence (76$0.77–$0.90 per kg H2 for a 60-day roundtrip and$0.09–$0.10 per kg H2 for a 7-day roundtrip. It is important to note that both routes rely heavily on laboratory scale data and the corresponding assumptions that stem from this limitation. Therefore, this research can serve as a guide to future experimental studies into validating the key assumptions made for this analysis.</p

Plant lectins: the ties that bind in root symbiosis and plant defense

Lectins are a diverse group of carbohydrate-binding proteins that are found within and associated with organisms from all kingdoms of life. Several different classes of plant lectins serve a diverse array of functions. The most prominent of these include participation in plant defense against predators and pathogens and involvement in symbiotic interactions between host plants and symbiotic microbes, including mycorrhizal fungi and nitrogen-fixing rhizobia. Extensive biological, biochemical, and molecular studies have shed light on the functions of plant lectins, and a plethora of uncharacterized lectin genes are being revealed at the genomic scale, suggesting unexplored and novel diversity in plant lectin structure and function. Integration of the results from these different types of research is beginning to yield a more detailed understanding of the function of lectins in symbiosis, defense, and plant biology in general

Dielectric relaxation in dipolar solid rotator phases

Dielectric relaxation in orientationally disordered dipolar solids often exhibits exotic features, such as a strong Cole-Cole relaxation for simple molecular solids. However, there does not seem to exist a detailed molecular theory of such phenomena. In this article, a molecular hydrodynamic theory of dielectric relaxation in solid rotator phases, such as plastic crystals, is presented

R.f. plasma-assisted deposition of diamond-like carbon films from methanol-water vapour mixture

Carbon films have been deposited in a parallel-plate r.f. CVD reactor using methanol-water vapour mixture as precursor, without any carrier or diluent gas. The various characterization tests showed that the films obtained at the optimum experimental conditions are typical DLC material. The notable feature of the experiment is that factors such as complexity of the set-ups, safety measures against hazards and costly precursor/carrier gases are avoided. This demonstration appears to be a positive step towards the more economical and convenient synthesis of DLC

Efflux pumps in drug resistance of Candida

The incidences of human pathogenic yeast Candida albicans and its related species acquiring resistance to antifungals have increased considerably, which poses serious problems towards its successful chemotherapy. The resistance of these pathogenic fungi is not restricted to the commonly used triazole compounds but is even encountered, though not often, with polyene derivatives as well. The efflux pump proteins belonging to ABC (ATP Binding Cassette) and MFS (Major Facilitators) super family are the most prominent contributors of multidrug resistance (MDR) in yeasts. The abundance of the drug transporters and their wider specificity suggest that these transporters may not be exclusively drug exporters in yeasts and may have other cellular functions. In this article we focus on some of the recent advances on the structure and function, evolution and transcriptional control of drug efflux proteins of Candida. A short discussion on the physiological relevance of drug transporters is also included

Studies on the optimisation of unbalanced magnetron sputtering cathodes

The optimisation is reported on the design of unbalanced magnetron (UBM) sputtering cathodes. For the study, a planar circular cathode backed by a double-coil electromagnet (compatible for a 100 mm diameter target) was developed. The variation of the structure and strength of the magnetic field in front of the target was investigated for different current combinations in the electromagnetic coils, and its effect on the sputtering process was analysed. The observations on the magnetic field geometry revealed some interesting features, such as the balancing point of the fields along the axis (null-point), and the zero axial region over the target surface (B-z = 0 ring). The positions of both could be controlled by adjusting the ratio of the electric current in the coils. The magnetic field null-point could be used as a reference for the region of homogeneous film growth. The B-z = 0 ring was the location where the glow discharge concentrated (or where the maximum target erosion occurred). The diameter of the ring determined the area covered by the discharge and thus the sputtering efficiency. The optimum substrate position can be fixed according to the position of the null-point and optimisation of sputtering can be achieved by adjusting the diameter of the B-z = 0 ring. The results of this study should be helpful in the designing of an ideal UBM using permanent magnets as well as electromagnets. (C) 1999 Elsevier Science Ltd. All rights reserved

Plasma surface modification of polystyrene and polyethylene

Polystyrene (PS) and polyethylene (PE) samples were treated with argon and oxygen plasmas. Microwave electron cyclotron resonance (ECR) was used to generate the argon and oxygen plasmas and these plasmas were used to modify the surface of the polymers. The samples were processed at different microwave powers and treatment time and the surface modification of the polymer was evaluated by measuring the water contact angle of the samples before and after the modification.Decrease in the contact angle was observed with the increase in the microwave power for both polystyrene and polyethylene. Plasma parameters were assessed using Langmuir probe measurements. Fourier transform infrared spectroscopy showed the evidence for the induction of oxygen-based functional groups in both polyethylene and polystyrenewhen treated with the oxygen plasma. Argon treatment of the polymers showed improvement in the wettability which is attributed to the process called as CASING, on the other hand the oxygen plasma treatment of the polymers showed surface functionalization. Correlation between the plasma parameters and the surface modification of the polymer is also discussed