Characterization of the collagen–vinyl graft copolymers prepared by the ceric ion method. I. Solution properties

Graft copolymerization of vinyl monomers on to collagen was carried out by the ceric ion method. The grafted vinyl polymer chains were isolated by both acid and enzymatic hydrolysis of the collagen backbone in order to characterize the graft copolymers. Proof of grafting was obtained through the detection of amino acid endgroups in the grafts isolated by both the methods. The grafts isolated gave the characteristic blue color normally associated with the presence of amino acids. The presence of amino acid endgroups was further confirmed by dinitrophenylation of the isolated grafts. The absorption spectra of the dinitrophenylated(DNP) grafts showed absorption maximum in the ultraviolet region of 340–360 mμ, characteristic of DNP-amino acids. Soluble collagen grafted with polyacrylamide(PAA) formed fibrils on heating to 37°C at neutral pH but, unlike the native collagen, these fibrils did not redissolve on cooling at 2°C. These results show that the redispersion property of soluble collagen was impaired, probably by attachment of the PAA side chains to the collagen molecule. The turbidimetric titration behavior of the grafts, their general behavior of swelling in different solvents, and the intrinsic viscosity of the copolymers in mixed solvents also provided additional proof of grafting.     

Synthesis and Characterization of Poly[N-Vinyl-2-Pyrrolidone-Polyethylene Glycol Diacrylate] Copolymeric Hydrogels for Drug Delivery

Abstract

Novel polymeric biodegradable and biocompatible copolymeric hydrogels based on N-vinyl-2-pyrrolidone (NVP) and polyethylene glycol diacrylate (PAC) were designed and synthesized. PAC macromonomer was synthesized by a modified procedure and characterized. Poly[N-vinyl-2-pyrrolidone-polyethylene glycol diacrylate] (Poly[NVP-PAC]) hydrogels were synthesized by varying the concentration of PAC. Azobisisobutyronitrile (AIBN) was used as the free radical initiator and N,N¹-methylene bis(acryl-amide) (BIS) was employed as the crosslinking agent. These hydrogels were characterized by various spectroscopic techniques. Fourier transform-infrared spectroscopy (FT-IR) confirms the formation of copolymer. Thermogravimetric analysis (TGA) curves obtained were continuous indicating the formation of copolymer. The glass transition temperature (T_g) of the copolymer was measured using differential scanning calorimetry (DSC). The equilibrium swelling measurements were carried out in simulated gastric and intestinal fluids (SGF & SIF). These swelling studies indicated that these gels had a higher sorption capacity in SIF when compared to that in SGF. 5-Fuorouracil (5-FU), an anti-cancer drug was entrapped in these hydrogels and the in-vitro release profiles were established in a sequential manner in SGF and SIF. About 50–56% of the drug entrapped was released in a period of 10 days.     

Oxidative amidation of benzyl alcohols with amino acid esters mediated by N-hydroxysuccinimide/phenyliodine diacetate

A simple protocol involving metal-free oxidative amidation of benzyl alcohols with amino acid esters has been presented. The amidation proceeds in a radical pathway unlike in conventional metal-mediated extrusion of dihydrogen. The method is advantageous in terms of metal-free conditions, nonexpensive commercial starting substrates. Also various substituents in the starting materials are tolerated and sterically hindered amino acid side chains could provide good yields of amide products.     

Cerimetric determination of uranium Use of triphenylmethane dyes as internal indicators

The use of the triphenylmethane dyes (erioglaucine, eriogreen, and xylene cynol FF) as internal indicators in the cerimetric titration of uranium^IV has been investigated. The titration is possible in the cold with sufficient rapidity and accuracy, the indicator colour change appearing sharply at the equivalence point. The indicator reactions are rapid and reversible within a wide range of acidity, from 0.5N to 8.0N, unlike other indicators, e.g. diphenylbenzidine, -phenylanth-ranilic acid or ferroïn, which require specified conditions for their proper functioning. These indicators can also beused for titration of uranium^IV with eerie ammonium nitrate in perchloric acid medium (but not in nitric acid medium).     

Image encryption based on permutation-substitution using chaotic map and Latin Square Image Cipher

In this paper we presented a image encryption based on permutation-substitution using chaotic map and Latin square image cipher. The proposed method consists of permutation and substitution process. In permutation process, plain image is permuted according to chaotic sequence generated using chaotic map. In substitution process, based on secrete key of 256 bit generate a Latin Square Image Cipher (LSIC) and this LSIC is used as key image and perform XOR operation between permuted image and key image. The proposed method can applied to any plain image with unequal width and height as well and also resist statistical attack, differential attack. Experiments carried out for different images of different sizes. The proposed method possesses large key space to resist brute force attack.     

A fluorescence test for vanadium(V) with resorcinol

Summary In continuation of our previous work in which salicylic acid was reported to give a very sensitive and an almost specific colour reaction with vanadium(V), we have now found that vanadium(V) reacts with resorcinol in 20 N sulphuric or phosphoric acid solution to give a blue coloured product, which gives a vivid red fluorescence under filtered ultraviolet light. A sensitive test for vanadium(V) has now been developed making use of this red fluorescence or of the bright blue colour. Dichromate gives a somewhat less sensitive violet colour with the resorcinol reagent under the same conditions, but the product does not fluoresce. Manganese(VII), cerium(IV), iron(III), titanium(IV), uranium(VI), molybdenum(VI) and tungsten(VI) do not interfere with the colour reaction or the fluorescence test for vanadium(V).     

Titration of cerium (IV) sulphate with sodium oxalate at the room temperature using ferroin as internal indicator

Summary A method has been developed for the titration of cerium(IV) sulphate with sodium oxalate at the room temperature, using ferroin as internal indicator. A new principle has been utilised for facilitating the indicator action at the equivalence point. This involves the use of a photochemical reaction between the oxalate and iron(III) which is deliberately added to the mixture containing cerium(IV) sulphate and ferriin. When the mixture is titrated with the sodium oxalate solution under exposure to the light from a Philips Repro lamp, the addition of a very slight excess of sodium oxalate solution, after all the cerium(IV) sulphate has reacted, produces a vivid red colour. The slight excess of sodium oxalate added reacts with the iron(III) salt photochemically producing a trace of iron(II) salt which reduces the ferriin to the red ferroin. In titrations with 0.1 and 0.05 N solutions of sodium oxalate, the error is negligible. In titrations with sodium oxalate solution of lower strengths, the error amounts to 0.02 ml of 0.01 N oxalate which has to be subtracted from the titre.     

Acid-mediated cyclizations of SEM-protected heterocyclic anilines and adjacent hydroxyls or enol-ethers

Acid-mediated cyclizations of SEM-protected heterocyclic anilines and adjacent hydroxyls or enol ethers during SEM deprotection are reported. Strategies to suppress these side reactions and their potential synthetic utilities are also described.