Hydrophobic amino acid

Pseudo-peptidic polymers have been synthesised by grafting l-valine (PV), l-leucine (PL) and l-phenylalanine (PP) onto the pendant carboxylic acid moieties of a pH-responsive polyamide, poly(l-lysine isophthalamide). The pH-responsive aqueous solution properties of PV-75, PL-75 and PP-75 with a stoichiometric degree of substitution of 75 mol% have been compared with those of the parent poly(l-lysine isophthalamide) using UV-visible and fluorescence spectroscopy. At low concentrations (≤0.1 mg mL-1), the grafted polymers displayed pH-dependent conformation. The pH at the onset of hydrophobic association (pHh) and the pH range over which association occurred varied significantly between the different amino acid grafts. The pHh values of PV-75, PL-75 and PP-75 at 0.025 mg mL-1 were 6.2, 7.0 and 7.2, respectively. Increasing concentration enhanced intermolecular aggregation. A bis-functional Cy5 derivative, incorporated within the backbones of poly(l-lysine isophthalamide) (polyCy5) and , was demonstrated to act as a fluorescence reporter on the state of polymer conformation and aggregation. The intracellular trafficking of PDP-75, examined by confocal microscopy, indicates potential applications of the grafted polymers in drug delivery and medical imaging.

pH-responsive polymers have been synthesised by grafting L-valine (PV-75), L-leucine (PL-75) and L-phenylalanine (PP-75) onto the pendant carboxylic acid moieties of a pseudo-peptide, poly(Llysine iso-phthalamide), at a stoichiometric degree of substitution of 75 mol%. The effect of such modification on the pH-, concentration-and time-dependent cell membrane-disruptive activity of the grafted polymers has been investigated using a haemolysis model. At 0.025 mg mL −1 , the grafted polymers were almost non-haemolytic at pH 7.4, but mediated considerable membrane lysis after 60 min in the pH range characteristic of early endosomes, which ranked in the order: PP-75 > PL-75 > PV-75 > poly(L-lysine iso-phthalamide). PP-75 was 35-fold more lytic on a molar basis than the membrane-lytic peptide melittin. With increasing concentration, the grafted polymers showed an increased ability to lyse cell membranes and caused noticeable membrane disruption at physiological pH. The mechanism of the polymer-mediated membrane destabilisation has been investigated. The in-vitro cytotoxicity of the grafted polymers has been assessed using a propidium iodide fluorescence assay. It has been demonstrated by confocal microscopy that the grafted polymers can induce a significant release of endocytosed materials into the cytoplasm of HeLa cells, which is a feature critical for drug delivery applications.

Angelwing clam (Pholas orientalis) hydrolysate was prepared by hydrolysis using bromelain. The hydrolysate named as bromelain hydrolysate (BH) was then treated with β-cyclodextrin in the ratio of 1:0.8 (v/w) by physical mixing and kneading methods producing the physical mixed hydrolysate (PMH) and kneaded method hydrolysate (KMH), respectively. The masking effect of β-cyclodextrin on bitterness was evaluated based on sensory analysis, amino acid analysis and determination of flavor compound by gas chromatographymass spectrometry (GC-MS) and field emission scanning electron microscope (FESEM). Sensory analysis showed that KMH has least bitter taste compared to BH. Amino acids analysis showed that hydrophobic amino acids content that contributed to the bitter taste were lower in KMH and PMH compared to BH. GC-MS analysis also showed that benzothiazole compounds were present in KMH. The absence of benzene, 1-phenyl-4-2-(2-cyano-2-phenylethyl) in KMH and PMH indicated that phenylalanine...

Angelwing clam (Pholas orientalis) hydrolysate was prepared by hydrolysis using bromelain. The hydrolysate named as bromelain hydrolysate (BH) was then treated with β-cyclodextrin in the ratio of 1:0.8 (v/w) by physical mixing and kneading methods producing the physical mixed hydrolysate (PMH) and kneaded method hydrolysate (KMH), respectively. The masking effect of β-cyclodextrin on bitterness was evaluated based on sensory analysis, amino acid analysis and determination of flavor compound by gas chromatography-mass spectrometry (GC-MS) and field emission scanning electron microscope (FESEM). Sensory analysis showed that KMH has least bitter taste compared to BH. Amino acids analysis showed that hydrophobic amino acids content that contributed to the bitter taste were lower in KMH and PMH compared to BH. GC-MS analysis also showed that benzothiazole compounds were present in KMH. The absence of benzene, 1-phenyl-4-2-(2-cyano-2-phenylethyl) in KMH and PMH indicated that phenylalanine in BH had been masked by β-cyclodextrin. FESEM showed that the new solid phase formed by kneading method has a crystal structure which was completely different from the original morphology of BH and β-cyclodextrin. Therefore, the bitterness in BH had successfully been masked by β-cyclodextrin, thus indicates its potential to be used as food ingredient..