Controlling the rate of softening to extend shelf life was a key target for researchers engineering genetically modified (GM) tomatoes in the 1990s, but only modest improvements were achieved. Hybrids grown nowadays contain 'non-ripening mutations' that slow ripening and improve shelf life, but adversely affect flavor and color. We report substantial, targeted control of tomato softening, without affecting other aspects of ripening, by silencing a gene encoding a pectate lyase.
This article incorporates recent research regarding time management into a model of work-family conflict. The authors hypothesized that 3 types of time management behavior would have both direct and indirect (through perceived control of time) relationships, with work interfering with family and family interfering with work. It was also hypothesized that both of these types of work-family conflict would be related to the strain outcomes of job dissatisfaction and health complaints. This model was tested with a sample of 522 workers. In general, the hypothesized relationships were supported.
Sedimentation equilibrium (analytical ultracentrifugation) is one of the most inherently suitable methods for the determination of average molecular weights and molecular weight distributions of polymers, because of its absolute basis (no conformation assumptions) and inherent fractionation ability (without the need for columns or membranes and associated assumptions over inertness). With modern instrumentation it is also possible to run up to 21 samples simultaneously in a single run. Its application has been severely hampered because of difficulties in terms of baseline determination (incorporating estimation of the concentration at the air/solution meniscus) and complexity of the analysis procedures. We describe a new method for baseline determination based on a smart-smoothing principle and built into the highly popular platform SEDFIT for the analysis of the sedimentation behavior of natural and synthetic polymer materials. The SEDFIT-MSTAR procedure – which takes only a few minutes to perform - is tested with four synthetic data sets (including a significantly non-ideal system) a naturally occurring protein (human IgG1) and two naturally occurring carbohydrate polymers (pullulan and λ–carrageenan) in terms of (i) weight average molecular weight for the whole distribution of species in the sample (ii) the variation in “point” average molecular weight with local concentration in the ultracentrifuge cell and (iii) molecular weight distribution.
Chitosans and pectins are natural polysaccharides which show great potential in drug delivery systems.Chitosans are a family of strongly polycationic derivatives of poly-N-acetyl-Dglucosamine. This positive charge is very important in chitosan drug delivery systems as it plays a very important role in mucoadhesion (adhesion to the mucosal surface). other chitosan based drug delivery systems involve complexation with ligands to form chitosan nanoparticles with can be used to encapsulate active compounds.Pectins are made of several structural elements the most important of which are the homogalacturonan (HG) and type I rhamnogalacturonan (RG-I) regions often described in simplified terms as the "smooth" and "hairy" regions respectively. Pectin HG regions consist of poly-glacturonic acid residues which can be partially methyl esterified. Pectins with a degree of methyl esterification (DM) > 50% are known as high methoxyl (HM) pectins and consequently low methoxyl (lM) pectins have a DM < 50%. low methoxyl pectins are of particular interest in drug delivery as they can form gels with calcium ion (Ca 2+ ) which has potential applications especially in nasal formulations.Biotechnology and Genetic Engineering Reviews -Vol. 27, 257-284 (2010) Polysaccharide drug delivery systems based on pectin and chitosan Chitosans are a family of strongly polycationic derivatives of poly-N-acetyl-Dglucosamine. This positive charge is very important in chitosan drug delivery systems as it plays a very important role in mucoadhesion (adhesion to the mucosal surface). Other chitosan based drug delivery systems involve complexation with ligands to form chitosan nanoparticles with can be used to encapsulate active compounds.Pectins are made of several structural elements the most important of which are the homogalacturonan (HG) and type I rhamnogalacturonan (RG-I) regions often described in simplified terms as the "smooth" and "hairy" regions respectively. Pectin HG regions consist of poly-glacturonic acid residues which can be partially methyl esterified. Pectins with a degree of methyl esterification (DM) > 50% are known as high methoxyl (HM) pectins and consequently low methoxyl (LM) pectins have a DM <50%. Low methoxyl pectins are of particular interest in drug delivery as they can form gels with calcium ion (Ca') which has potential applications especially in nasal formulations.
VanA-type resistance to glycopeptide antibiotics in clinical enterococci is regulated by the VanSARA two-component signal transduction system. The nature of the molecular ligand that is recognised by the VanSA sensory component has not hitherto been identified. Here we employ purified, intact and active VanSA membrane protein (henceforth referred to as VanS) in analytical ultracentrifugation experiments to study VanS oligomeric state and conformation in the absence and presence of vancomycin. A combination of sedimentation velocity and sedimentation equilibrium in the analytical ultracentrifuge (SEDFIT, SEDFIT-MSTAR and MULTISIG analysis) showed that VanS in the absence of the ligand is almost entirely monomeric (molar mass M = 45.7 kDa) in dilute aqueous solution with a trace amount of high molar mass material (M ~ 200 kDa). The sedimentation coefficient s suggests the monomer adopts an extended conformation in aqueous solution with an equivalent aspect ratio of ~(12 ± 2). In the presence of vancomycin over a 33% increase in the sedimentation coefficient is observed with the appearance of additional higher s components, demonstrating an interaction, an observation consistent with our circular dichroism measurements. The two possible causes of this increase in s – either a ligand induced dimerization and/or compaction of the monomer are considered.
Chitosan nanoparticles prepared by ionotropic gelation with the tripolyphosphate (TPP) polyanion have been widely considered for drug delivery. The stability (shelf-life) of TPP-chitosan nanoparticles is highly relevant to its potential use as a drug delivery agent as this plays an important role in the function of the nanoparticle and will determine shelf-life. In the present study, the physical stability (in terms of particle size) of TPP-chitosan nanoparticles was measured across a range of different temperature conditions: 4 ºC, 25 ºC and 40 ºC using differential sedimentation. After 12 months storage at 4 and 25 °C the size of nanoparticles remained similar to those of the freshly prepared samples, whilst after storage at 40 °C there were little or no TPP-chitosan nanoparticles remaining after only 6 months. This may be due to the decrease in molar mass of the chitosan possibly due to hydrolysis causing scission of the polymer chains, which results in a decrease in nanoparticle size and eventual disintegration. This mechanism is important in the application of TPP-chitosan as a drug delivery agent.
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