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At least 811 records · Page 45Linked to original sources
PubMed1998

In vitro myotoxicity of selected cationic macromolecules used in non-viral gene delivery.

PURPOSE: Cationic lipid/DNA complexes have been proposed as a method of in vivo gene delivery via intravenous or intramuscular injection. A concern with using these polycationic molecules is whether they are associated with tissue toxicity at the injection site. Therefore, the objective of these studies was to investigate the myotoxic potential of selected non-viral gene delivery macromolecules (e.g., cationic lipids and polymers) with and without plasmid DNA (pDNA) in vitro. METHODS: Myotoxicity was assessed by the cumulative release of creatine kinase (CK) over 90 minutes from the isolated rodent extensor digitorum longus muscle into a carbogenated balanced salt solution (BBS, pH 7.4, 37 degrees C) following a 15 microL injection of the test formulation. Phenytoin (Dilantin) and normal saline served as positive and negative controls, respectively. RESULTS: The myotoxicity of plasmid DNA (pDNA, approximately 5000bp, 1 mg/ml) was not statistically different from normal saline. However, the myotoxicity of Dilantin was 16-times higher than either normal saline or pDNA (p < 0.05). Cationic liposomes were found to be less myotoxic than polylysine and PAMAM dendrimers. Polylysine's myotoxicity was found to be dependent upon concentration and molecular weight. The myotoxicity of formulations of cationic liposomes(s), lower molecular weight polylysine (25,000) and higher concentration of PAMAM dendrimers with pDNA were found to be statistically less significant than those formulations without pDNA. CONCLUSIONS: The cationic liposomes were less myotoxic compared to the dendrimers and polylysine. Myotoxicity was dependent upon the type of cationic lipid macromolecule, concentration, molecular weight and the presence of pDNA. A possible explanation for this reduced tissue damage in cationic lipids complexed with pDNA is that the formation of complex reduces the overall positive charge of the injectable system resulting in less damage.

Animals↗
PubMed2003

Physicochemical properties of liposomes affecting apoptosis induced by cationic liposomes in macrophages.

PURPOSE: Cationic liposomes are expected to be useful as nonviral vectors for gene delivery. Cationic liposomes showed cytotoxicity, and we proposed that the cytotoxicity is through apoptosis. In this study, we examined the effects of liposomal properties, such as liposomal charge, size, membrane fluidity, and PEG coating, on the induction of apoptosis in the macrophage-like cell line RAW264.7. METHODS: RAW264.7 cells were treated with liposomes, and the induction of apoptosis was evaluated by monitoring the changes in DNA content by flow cytometry. The association of liposomes with cells and the generation of reactive oxygen species (ROS) were also measured by flow cytometry. RESULTS: The induction of apoptosis of RAW264.7 cells was dependent on the concentrations of stearylamine or cholesterol, a component of cationic liposomes. A significant correlation was observed between the degree of apoptosis and association of cationic liposomes with the cells. Coating the liposomal surface with polyethylene glycol (PEG) decreased the association of cationic liposomes with RAW264.7 cells and reduced the induction of apoptosis. Liposomal size also affected the induction of apoptosis, and larger liposomes showed a higher degree of apoptosis induction. Furthermore, ROS, which were required for the induction of apoptosis by cationic liposomes, were generated in a cholesterol content-dependent manner, and ROS generation was also decreased by PEG coating as the association and the induction of apoptosis were reduced. CONCLUSIONS: The degree of apoptosis is related to the extent of association of cationic liposomes with cells and is related to the generation of ROS.

Animals↗
PubMed2004

pH dependence of the efficiency of binding of iron cations to the donor side of photosystem II.

Light-induced interaction of Fe(II) cations with the donor side of Mn-depleted photosystem II (PS II(-Mn)) results in the binding of iron cations and blocking of the high-affinity (HAZ) Mn-binding site. The pH dependence of the blocking was measured using the diphenylcarbazide/2,6-dichlorophenolindophenol test. The curve of the pH dependence is bell-shaped with pK1 = 5.8 and pK2 = 8.0. The pH dependence of the O2-evolution mediated by PS II membranes is also bell-shaped (pK2 = 7.6). The pH dependence of the process of electron donation from exogenous donors in PS II(-Mn) was studied to determine the location of the alkaline pH sensitive site of the electron transport chain. The data of the study showed that the decrease in the iron cation binding efficiency at pH > 7.0 during blocking was determined by the donor side of the PS II(-Mn). Mössbauer spectroscopy revealed that incubation of PS II(-Mn) membranes in a buffer solution containing 57Fe(II) + 57Fe(III) was accompanied by binding only Fe(III) cations. The pH dependence of the nonspecific Fe(III) cation binding is also described by the same bell-shaped curve with pK2 = 8.1. The treatment of the PS II(-Mn) membranes with the histidine modifier diethylpyrocarbonate resulted in an increase in the iron binding strength at alkaline pH. It is suggested that blocking efficiency at alkaline pH is determined by competition between OH- and histidine ligand for Fe(III). Because the high-affinity Mn-binding site contains no histidine residue, this fact can be regarded as evidence that histidine is located at another (other than high-affinity) Fe(III) binding site. In other words, this means that the blockage of the high-affinity Mn-binding site is determined by at least two iron cations. We assume that inactivation of oxygen-evolving complex and inhibition of photoactivation in the alkaline pH region are also determined by competition between OH- and a histidine residue involved in coordination of manganese cation outside the high-affinity site.

Cations↗
PubMed1993

Co-existence of cationic and chloride components in odorant-induced current of vertebrate olfactory receptor cells.

Odorant stimulation leads to a depolarization of olfactory receptor neurons. A mechanism underlying this transduction, which occurs in the sensory cilia, involves a G-protein-mediated increase in adenylyl cyclase activity, and therefore a rise in internal cyclic AMP and consequent opening of a cAMP-gated cation channel on the plasma membrane. Another mechanism, not as well established, involves the opening of an inositol trisphosphate-activated cation channel on the plasma membrane as a result of phospholipase C activity. In both cases, an influx of cations is thought to generate the depolarizing receptor potential. We now report, however, that the mechanism is actually more complex. The odorant-induced current appears to contain an inward chloride component also, which is triggered by calcium influx through the cation-selective channel. This newly found chloride component can be as large as the cationic component. The co-existence of cationic and chloride components in the odorant response, possibly unique among sensory transduction mechanisms, may serve to reduce variations in the transduction current resulting from changes in external ionic concentrations around the olfactory cilia. Our finding can explain the long-standing puzzle of why removal of most mucosal cations still does not diminish the amplitude of the olfactory receptor cell response.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1974

The influx of calcium ions into human erythrocytes during cold storage. The influences of extracellular pH, intracellular adenosine triphosphate and efflux of univalent cations.

1. When human erythrocytes are stored at 3 degrees C for several days as a suspension in iso-osmotic sucrose or KCl, containing CaCl(2), the rates of cellular ATP degradation are similar. 2. During cold storage of erythrocytes in sucrose-CaCl(2) medium, Ca(2+) influx and univalent-cation efflux occur, the pH value of the suspending medium rises and the intracellular pH falls. These pH changes correlate reasonably well with alterations in the membrane potential calculated from Cl(-) distribution. 3. The presence of Ca(2+) in the medium does not increase the rate of univalent-cation efflux from the cells. 4. When the pH of the medium is raised by addition of buffers, the rates of both Ca(2+) influx and univalent-cation efflux increase. 5. Replacement of sucrose by KCl as the main osmotic component of the medium completely suppresses Ca(2+) influx and univalent-cation efflux, although the pH of the KCl medium is higher than that of the sucrose medium. 6. When sucrose is replaced by choline chloride, Ca(2+) influx and univalent-cation efflux still occur, and the pH of the medium is similar to that found in iso-osmotic KCl. 7. When valinomycin, Pb(2+) or Cd(2+) are added to the iso-osmotic sucrose medium, the rate of efflux of univalent cations increases as also does the influx of Ca(2+). 8. From these and other observations, it was concluded that it is univalent-cation efflux rather than ATP depletion or elevated extracellular pH which is the prerequisite for Ca(2+) influx during cold storage.

Adenosine Triphosphate↗
PubMed1980

Interrelationship between anionic and cationic forms of glutathione S-transferases of human liver.

Human liver glutathione S-transferases (GSH S-transferases) were fractionated into cationic and anionic proteins. During fractionation with (NH4)2SO4 the anionic GSH S-transferases are concentrated in the 65%-saturated-(NH4)2SO4 fraction, whereas the cationic GSH S-transferases separate in the 80%-saturated-(NH4)2SO4 fraction. From the 65%-saturated-(NH4)2SO4 fraction two new anionic GSH S-transferases, omega and psi, were purified to homogeneity by using ion-exchange chromatography on DEAE-cellulose, Sephadex G-200 gel filtration, affinity chromatography on GSH bound to epoxy-activated Sepharose and isoelectric focusing. By a similar procedure, cationic GSH S-transferases were purified from the 80%-saturated-(NH4)2SO4 fraction. Isoelectric points of GSH S-transferases omega and psi are 4.6 and 5.4 respectively. GSH S-transferase omega is the major anionic GSH S-transferase of human liver, whereas GSH S-transferase psi is present only in traces. The subunit mol.wt. of GSH S-transferase omega is about 22500, whereas that of cationic GSH S-transferases is about 24500. Kinetic and structural properties as well as the amino acid composition of GSH S-transferase omega are described. The antibodies raised against cationic GSH S-transferases cross-react with GSH S-transferase omega. There are significant differences between the catalytic properties of GSH S-transferase omega and the cationic GSH S-transferases. GSH peroxidase II activity is displayed by all five cationic GSH S-transferases, whereas both anionic GSH S-transferases do not display this activity.

Amino Acids↗
PubMed2003

Oxidation of thioanisole and p-methoxythioanisole by lignin peroxidase: kinetic evidence of a direct reaction between compound II and a radical cation.

The reaction of H2O2 with thioanisole and p-methoxythioanisole catalysed by lignin peroxidase from Phanerochaete chrysosporium has been studied spectrophotometrically under turnover and single turnover conditions with a stopped-flow apparatus. Pre-formed lignin peroxidase compounds I and II are each able to react with the sulphides to form a sulphide radical cation. The radical cation is then converted into the sulphoxide either by reaction with the medium or by reaction with compound II. This is the first report of a direct reaction between compound II and the substrate radical cation. With thioanisole, significant enantiomeric selectivity and high oxygen incorporation in the sulphoxide are obtained because compound II is preferentially reduced by the enzyme-bound thioanisole radical cation compared with the neutral substrate. By contrast, with p-methoxythioanisole, the data imply formation of an intermediate ternary complex comprising compound II, radical cation and neutral substrate, such that a chain of electron transfer reactions starting from neutral molecule and progressing to oxidized haem via substrate radical cation is facilitated, yielding the native enzyme and two molecules of p-methoxythioanisole radical cation as products. The reactions of compounds I and II with sulphides imply flexing of the apoprotein moiety during catalysis.

Cations↗
PubMed1987

Effect of cations and temperature on kinetics of desmin assembly.

Smooth-muscle desmin, which was isolated from avian gizzard, was purified and used to form reconstituted intermediate filaments. Filament assembly was done in the presence of physiological cations, Ca2+, Mg2+, Na+, and Na+ plus Mg2+, and with non-physiological cations Cu2+ and Ni2+. Assembly was done at 2 degrees, 22 degrees and 37 degrees C, and was monitored by absorbance and by electron microscopy. Absorbance increased most rapidly during the first 2-5 min and then increased at a slower rate with the physiological cations, but decreased after that time with the non-physiological cations. For each physiological cation, absorbance increased with increasing temperature. This was particularly evident with Ca2+, which produced the lowest absorbance at 2 degrees C and the highest at 37 degrees C. When ionic strength was comparable, filament-forming buffers that contained bivalent cations were associated with higher absorbance values. Filament diameters were significantly smaller 60 min after assembly initiation than after 5 min. Average filament diameters, when formed in the presence of Cu2+ or Ni2+, were 10% greater than in the presence of the physiological cations and did not show a consistent tendency to decrease as time increased. These results demonstrate the importance, not only of the pH and ionic composition of the filament-forming buffer, but also of the temperature and duration of dialysis for reconstitution of desmin filaments.

Animals↗
PubMed1984

Plasma clearance, tissue distribution and catabolism of cationized albumins with increasing isoelectric points in the rat.

The infusion of cationic substances produces acute renal failure and proteinuria, and an experimental disease very similar to disseminated coagulopathy. The purpose of this work was to investigate further, in the rat, the plasma disappearance rate, the tissue distribution and the catabolism of albumins with modified isoelectric points. Human serum albumin was cationized with hexanediamine and labelled with 125I or 131I. During 10-180 min after their intravenous injection into the rat, these modified 125I-labelled albumins were cleared from the plasma at a rate which increased with their isoelectric point. At 1 and 3 h after the injection of highly cationic proteins (isoelectric point higher than 9.5) the tissue protein bound 125I concentration was greatest (approximately 3.5% of the injected activity/g) in the spleen and liver. A significant amount of the basic proteins was found in the kidney and in the lung (0.75-1%/g). Their concentration was much lower in other tissues. The whole body radioactivity was significantly lower 24 h after the injection of 131I-labelled cationized albumins than after similarly labelled native albumin. However, expressed as a percentage of the retention at 24 h, the body radioactivity at later times was higher for cationic than for native albumin. We conclude that cationized albumins are cleared from the plasma, mainly by the reticuloendothelial system, at a rate directly related to their isoelectric point. The cationized albumins are catabolized very rapidly initially, but a fraction of the injected protein remains in the body for a longer time than native albumin.

Animals↗
PubMed2002

Divalent cations and polyamines bind to loop 8 of 14-3-3 proteins, modulating their interaction with phosphorylated nitrate reductase.

Binding of 14-3-3 proteins to nitrate reductase phosphorylated on Ser543 (phospho-NR) inhibits activity and is responsible for the inactivation of nitrate reduction that occurs in darkened leaves. The 14-3-3-dependent inactivation of phospho-NR is known to require millimolar concentrations of a divalent cation such as Mg2+ at pH 7.5. We now report that micromolar concentrations of the polyamines, spermidine(4+) and spermine(3+), can substitute for divalent cations in modulating 14-3-3 action. Effectiveness of the polyamines decreased with a decrease of polycation charge: spermine(4+) > spermidine(3+) >>> cadavarine(2+) approximately putrescine(2+) approximately agmatine(2+) approximately N1-acetylspermidine(2+), indicating that two primary and at least one secondary amine group were required. C-terminal truncations of GF14 omega, which encodes the Arabidopsis 14-3-3 isoform omega, indicated that loop 8 (residues 208-219) is the likely cation-binding site. Directed mutagenesis of loop 8, which contains the EF hand-like region identified in earlier studies, was performed to test the role of specific amino acid residues in cation binding. The E208A mutant resulted in a largely divalent cation-independent inhibition of phospho-NR activity, whereas the D219A mutant was fully Mg(2+)-dependent but had decreased affinity for the cation. Mutations and C-terminal truncations that affected the Mg(2+) dependence of phospho-NR inactivation had similar effects on polyamine dependence. The results implicate loop 8 as the site of divalent cation and polyamine binding, and suggest that activation of 14-3-3s occurs, at least in part, by neutralization of negative charges associated with acidic residues in the loop. We propose that binding of polyamines to 14-3-3s could be involved in their regulation of plant growth and development.

14-3-3 Proteins↗
PubMed2005

Molecular-dynamics simulations of alkaline-earth metal cations in water by atom-bond electronegativity equalization method fused into molecular mechanics.

Intermolecular potential for alkaline-earth metal (Be(2+), Mg(2+), and Ca(2+)) cations in water has been derived using the atom-bond electronegativity equalization method fused into molecular mechanics (ABEEM/MM), and it is consistent with what was previously applied to the hydration study of the monovalent cations. Parameters for the effective interaction between a cation and a water molecule were determined, reproducing the ab initio results. The static, dynamic, and thermodynamic properties of Be(2+)(aq), Mg(2+)(aq), and Ca(2+)(aq) were studied using these potential parameters. Be(2+) requires a more complicated form of the potential function than Mg(2+) and Ca(2+) in order to obtain better fits. Strong influences of the twofold charged cations on the structures of the hydration shells and some other properties of aqueous ionic solutions are discussed and compared with the results of a previous study of monovalent cations in water. At the same time, comparative study of the hydration properties of each cation is also discussed. This work demonstrates that ABEEM/MM provides a useful tool in the exploration of the hydration of double-charged cations in water.

Algorithms↗
PubMed1995

Regulation of integrin alpha 5 beta 1-fibronectin interactions by divalent cations. Evidence for distinct classes of binding sites for Mn2+, Mg2+, and Ca2+.

Integrin-ligand interactions are known to be dependent on divalent cations, although the precise role of cations in ligand binding is still unclear. Using the interaction between alpha 5 beta 1 and fibronectin as a model system, we have performed a comprehensive analysis of the effects of Mn2+, Mg2+, and Ca2+ on ligand binding. Each cation had distinct effects on the ligand-binding capacity of alpha 5 beta 1:Mn2+ promoted high levels of ligand binding, Mg2+ promoted low levels of binding, and Ca2+ failed to support binding. Studies of the effects of different combinations of cations on ligand binding indicated that the cation-binding sites within alpha 5 beta 1 are not all identical, or of broad specificity, but instead each site shows a distinct preference for one or more cations. Ca2+ strongly inhibited Mn(2+)-supported ligand binding, but this inhibition was noncompetitive, suggesting that Ca2+ recognizes different cation-binding sites to Mn2+. In contrast, Ca2+ acted as a direct competitive inhibitor of Mg(2+)-supported ligand binding, implying that Ca2+ can displace Mg2+ from the integrin. However, low concentrations of Ca2+ greatly increased the apparent affinity of Mg2+ for its binding site, suggesting the existence of a distinct high affinity Ca(2+)-binding site. Taken together, our results imply that the ligand-binding capacity of alpha 5 beta 1 can be regulated in a complex manner through separate classes of binding sites for Mn2+, Mg2+, and Ca2+.

Animals↗
PubMed2001

Properties and regulation of organic cation transport in freshly isolated human proximal tubules.

The kidney, and more specifically the proximal tubule, is the main site of elimination of cationic endogenous metabolites and xenobiotics. Although numerous studies exist on renal organic cation transport of rat and rabbit, no information is available from humans. Therefore, we examined organic cation transport and its regulation across the basolateral membrane of isolated human proximal tubules. mRNA for the cation transporters hOCT1 and hOCT2 as well as hOCTN1 and hOCTN2 was detected in these tubules. Organic cation transport across the basolateral membrane of isolated collapsed proximal tubules was recorded with the fluorescent dye 4-(4-dimethylamino)styryl-N-methylpyridinium (ASP(+)). Depolarization of the cells by rising extracellular K(+) concentration to 145 mm reduced ASP(+) uptake by 20 +/- 5% (n = 15), indicating its electrogeneity. The substrates of organic cation transport tetraethylammonium (K(i) = 63 microm) and cimetidine (K(i) = 11 microm) as well as the inhibitor quinine (K(i) = 2.9 microm) reduced ASP(+) uptake concentration dependently. Maximal inhibition reached with these substances was approximately 60%. Stimulation of protein kinase C with 1,2-dioctanoyl-sn-glycerol (DOG, 1 microm) or ATP (100 microm) inhibited ASP(+) uptake by 30 +/- 3 (n = 16) and 38 +/- 13% (n = 6), respectively. The effect of DOG could be reduced with calphostin C (0.1 microm, n = 7). Activation of adenylate cyclase by forskolin (1 microm) decreased ASP(+) uptake by 29 +/- 3% (n = 10). hANP (10 nm) or 8-bromo-cGMP (100 microm) also decreased ASP(+) uptake by 17 +/- 3 (n = 9) or 32 +/- 5% (n = 10), respectively. We show for the first time that organic cation transport across the basolateral membrane of isolated human proximal tubules, most likely mediated via hOCT2, is electrogenic and regulated by protein kinase C, the cAMP- and the cGMP-dependent protein kinases.

Biological Transport↗
PubMed2003

Residue Asp-189 controls both substrate binding and the monovalent cation specificity of thrombin.

Residue Asp-189 plays an important dual role in thrombin: it defines the primary specificity for Arg side chains and participates indirectly in the coordination of Na(+). The former role is shared by other proteases with trypsin-like specificity, whereas the latter is unique to Na(+)-activated proteases in blood coagulation and the complement system. Replacement of Asp-189 with Ala, Asn, Glu, and Ser drastically reduces the specificity toward substrates carrying Arg or Lys at P1, whereas it has little or no effect toward the hydrolysis of substrates carrying Phe at P1. These findings confirm the important role of Asp-189 in substrate recognition by trypsin-like proteases. The substitutions also affect significantly and unexpectedly the monovalent cation specificity of the enzyme. The Ala and Asn mutations abrogate monovalent cation binding, whereas the Ser and Glu mutations change the monovalent cation preference from Na(+) to the smaller cation Li(+) or to the larger cation Rb(+), respectively. The observation that a single amino acid substitution can alter the monovalent cation specificity of thrombin from Na(+) (Asp-189) to Li(+) (Ser-189) or Rb(+) (Glu-189) is unprecedented in the realm of monovalent cation-activated enzymes.

Alanine↗
PubMed1996

An FTIR spectroscopic study of calf-thymus DNA complexation with Al(III) and Ga(III) cations.

The interaction of calf-thymus DNA with trivalent Al and Ga cations, in aqueous solution at pH = 6-7 with cation/DNA(P) (P = phosphate) molar ratios (r) 1/80, 1/40, 1/20, 1/10, 1/4 and 1/2 was characterized by Fourier Transform infrared (FTIR) difference spectroscopy. Spectroscopic results show the formation of several types of cation-DNA complexes. At low metal ion concentration (r = 1/80, 1/40), both cations bind mainly to the backbone PO2 group and the guanine N-7 site of the G-C base pairs (chelation). Evidence for cation chelate formation comes from major shifting and intensity increase of the phosphate antisymmetric stretch at 1222 cm-1 and the mainly guanine band at 1717 cm-1. The perturbations of A-T base pairs occur at high cation concentration with major helix destabilization. Evidence for cation binding to A-T bases comes from major spectral changes of the bands at 1663 and 1609 cm-1 related mainly to the thymine and adenine in-plane vibrations. A major reduction of the B-DNA structure occurs in favor of A-DNA upon trivalent cation coordination.

Aluminum↗
PubMed1998

Monte Carlo simulation of DNA fragment hydration in the presence of alkaline cations using novel atom-atom potential functions.

The set of atom-atom potential functions specially adjusted to simulation of nucleic acid fragment hydration (Poltev, Grokhlina & Malenkov, J. Biomol. Struct. Dyn. 2, 413, 1984) is extended by including alkaline cation interactions. The choice of new potential functions was realized using experimental data on crystal hydrates of nucleotides and related compounds as well as thermodynamic data on ion solutions. The extended set of potential functions allows to reproduce many features of interactions between alkaline cations and nucleic acid fragments in water solutions. The sites of preferential cation localization near bases and phosphate groups were obtained and examined. The potential functions reproduce the dissociation tendency of cation-phosphate group and cation-base complexes in aqueous medium. Pathways of cation dissociations from nucleic acid components have been studied, and metastable water-bridged positions of cations near bases and phosphate group have been revealed.

Cations, Monovalent↗
PubMed2003

Cationic liposomes for gene transfection.

Cationic liposomes spontaneously interact with the negatively charged DNA to form a stable complex that promotes the gene transfer to cells. The mode of formation and the size of cationic liposomes/DNA complexes were investigated using the atomic force microscopy (AFM). Also the most important physical-chemical factors involved in cationic liposome-mediated gene transfection, e.g. size and lipidic composition, were evaluated through the transfection of complexes with different liposomes/DNA molar ratio into three types of cultured cells. Cationic liposomes, composed of a neutral lipid (phosphatidilcoline), a cationic lipid dimethyldioctadecylammonium bromide (DDAB), a co-lipid 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine (DOPE) and a phospholipid derivative of polyethylene glycol (DSPE-mPEG) at different molar ratio, were mixed with a plasmid pCMVbeta to form liposomes/DNA complexes. We have demonstrated that the complexes were made by complicated structures in which the liposomes tend to aggregate and the DNA is surrounded by lipidic material. In vitro transfection efficiency by liposomes/plasmid pCMVbeta complexes was found to depend on the kind of lipid associated in the liposomes and the liposomes/DNA mixing ratio. The importance of associating DOPE in cationic liposomes was confirmed; this co-lipid is able to improve the ability of cationic liposomes to transfect cells but in addition, the AFM images and the EtBr fluorescence experiments have suggested that this lipid can also play an important role to facilitate the formation of stable liposomes, which efficaciously protect the DNA by nuclease digestion.

Animals↗
PubMed1999

Evaluation of the emulsifying properties of some cationic starches.

Different cationic potato, maize, and waxy maize starches were evaluated for their emulsifying properties. Emulsions were prepared using 20% (w/w) arachidic oil and 80% (w/w) water. Emulsions with the cationic starches as emulsifier in a concentration ranging from 1% to 5% (w/w) were prepared and characterized by droplet size and viscosity measurements, and the stability was evaluated visually and by electrical conductance measurements. None of the cationic potato, waxy maize starches, and maize starches with a low degree of substitution (DS) showed adequate emulsifying properties. Emulsions prepared using non-pregelatinized (C [symbol: see text] bond 05914, 2% and 5% w/w; C [symbol: see text] bond 05907, 5% w/w) and pregelatinized (C [symbol: see text] bond 12504, 5% w/w) cationic maize starches with high-DS were visually stable. The initial mean droplet volume diameter of the emulsions prepared with these cationic starches in a 5% (w/w) concentration was similar and ranged from 2.40 to 2.84 microns; however, there was an important difference in droplet size distribution. The droplet size distribution of the emulsions prepared using the non-pregelatinized high-DS cationic starches was markedly narrower than in the case of the emulsions prepared using the pregelatinized high-DS cationic starches. The droplet size of the emulsions remained almost constant during 120 days of storage. Visual inspection and electrical conductance measurements showed that these emulsions were stable for at least 120 days.

Cations↗