Kristberg Kristbergsson - Academia.edu (original) (raw)
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Papers by Kristberg Kristbergsson
Journal of Drug Targeting, 2000
The cationic polymer poly(2-(dimethylamino)ethyl methacrylate) (p(DMAEMA)) is able to efficiently... more The cationic polymer poly(2-(dimethylamino)ethyl methacrylate) (p(DMAEMA)) is able to efficiently bind and condense DNA and to mediate transfection of a variety of cell types. In this study, fluorescence activated cell sorting (FACS), confocal laser fluorescence microscopy (CSLM) and electron microscopy (EM) techniques were used to investigate in vitro the cellular interaction of p(DMAEMA)-based polyplexes with human ovarian carcinoma cells (OVCAR-3). Cellular association and subsequent internalization only occurred when the polyplexes exhibited a positive zeta potential. Small-sized polyplexes have an advantage over large-sized complexes regarding cellular entry. The effect of the presence of tertiary amine groups versus the presence of quatenary amine groups was evaluated by comparing p(DMAEMA) with its quaternary ammonium analogue poly(2-(trimethylamino)ethyl methacrylate) (p(TMAEMA)). The combined cellular interaction and transfection results suggest that the latter polymer does not have an intrinsic endosomal escape property, in contrast to the 'proton sponge' effect proposed for p(DMAEMA). PEGylation of p(DMAEMA) effectively shielded the surface charge and yielded a notably lower degree of cellular interaction. Data on the effects of the presence of endocytosis inhibitors and an endosome-disruptive peptide in the culture medium on the cellular interaction and transfection activity of p(DMAEMA)-based polyplexes support endocytosis as being the principal pathway for intracellular delivery of plasmid. Both the CLSM and EM studies did not reveal the presence of polyplexes or plasmid outside the endocytic vesicles or within the nucleus, suggesting that intracellular trafficking from the endosomes to the nucleus is a very inefficient process.
Journal of Aquatic Food Product Technology, Oct 15, 2008
J Aquat Food Prod Technol, 2002
... Address correspondence to: Jae W. Park at the above address. ... system, the recovered mince ... more ... Address correspondence to: Jae W. Park at the above address. ... system, the recovered mince from a Model 805 Ikeuchi me-chanical deboner (Ikeuchi Tekkosho, Ltd., Japan) was washed twice in cold water (< 5°C) for 5 min, using a water/meat ratio of 3:1 for the first wash and ...
Journal of Agricultural and Food Chemistry, Aug 9, 2006
The effect of sonication during chitin extraction from freshwater prawn shells on yield, purity, ... more The effect of sonication during chitin extraction from freshwater prawn shells on yield, purity, and crystallinity of chitin was investigated. Dry prawn shells were suspended for 4 h in 0.25 M HCl at 40 degrees C while they were sonicated for 0, 1, and 4 h. Demineralized shells were lyophilized, resuspended in 0.25 M NaOH, and sonicated again for 0, 1, and 4 h for protein removal. The yield of chitin decreased from 8.28 to 5.02% for nonsonicated and sonicated samples, respectively, which was attributed to losses of depolymerized materials in the wash water. The application of ultrasound enhanced the removal of proteins. In nontreated shells, the amount of protein was 44.01% and was reduced to 12.55, 10.59, and 7.45% after 0, 1, and 4 h of sonication treatments. The glucosamine content slightly decreased with sonication probably because of losses due to depolymerization. The crystallinity indices of chitins decreased as the time of sonication increased. The degree of acetylation of chitins was unaffected by sonication, but the degree of acetylation of chitosans produced from sonicated chitin decreased from 70.0 to 68.7 and 61.4% for 1 and 4 h sonicated samples, respectively.
Food Research International, 2015
Journal of Food Science, May 1, 2004
Cod fillets were injected with brine, then immersed in brine with the same composition as used fo... more Cod fillets were injected with brine, then immersed in brine with the same composition as used for injection, and finally frozen in a plate freezer. The composition of the brine varied with groups, containing phosphates (3%), salt (5%), and/or proteins (10%), soy protein concentrate, or hydrolyzed cod proteins. The fillets were stored at -24°C for 3 mo and then thawed to evaluate the effects on yield after thawing and cooking, drip, water-holding capacity, pH, and chemical composition. Addition of proteins slightly increased the yield of thawed fillets, but salt and phosphates were more effective. Comparison of the different proteins showed that fish proteins were not as effective as soy proteins with respect to the physicochemical parameters evaluated with the exception of water-holding capacity. The use of both type of proteins resulted in a negative appearance of the fillets, such as discoloration and slimy surface.
Journal of Drug Targeting, 2000
The cationic polymer poly(2-(dimethylamino)ethyl methacrylate) (p(DMAEMA)) is able to efficiently... more The cationic polymer poly(2-(dimethylamino)ethyl methacrylate) (p(DMAEMA)) is able to efficiently bind and condense DNA and to mediate transfection of a variety of cell types. In this study, fluorescence activated cell sorting (FACS), confocal laser fluorescence microscopy (CSLM) and electron microscopy (EM) techniques were used to investigate in vitro the cellular interaction of p(DMAEMA)-based polyplexes with human ovarian carcinoma cells (OVCAR-3). Cellular association and subsequent internalization only occurred when the polyplexes exhibited a positive zeta potential. Small-sized polyplexes have an advantage over large-sized complexes regarding cellular entry. The effect of the presence of tertiary amine groups versus the presence of quatenary amine groups was evaluated by comparing p(DMAEMA) with its quaternary ammonium analogue poly(2-(trimethylamino)ethyl methacrylate) (p(TMAEMA)). The combined cellular interaction and transfection results suggest that the latter polymer does not have an intrinsic endosomal escape property, in contrast to the 'proton sponge' effect proposed for p(DMAEMA). PEGylation of p(DMAEMA) effectively shielded the surface charge and yielded a notably lower degree of cellular interaction. Data on the effects of the presence of endocytosis inhibitors and an endosome-disruptive peptide in the culture medium on the cellular interaction and transfection activity of p(DMAEMA)-based polyplexes support endocytosis as being the principal pathway for intracellular delivery of plasmid. Both the CLSM and EM studies did not reveal the presence of polyplexes or plasmid outside the endocytic vesicles or within the nucleus, suggesting that intracellular trafficking from the endosomes to the nucleus is a very inefficient process.
Journal of Aquatic Food Product Technology, Oct 15, 2008
J Aquat Food Prod Technol, 2002
... Address correspondence to: Jae W. Park at the above address. ... system, the recovered mince ... more ... Address correspondence to: Jae W. Park at the above address. ... system, the recovered mince from a Model 805 Ikeuchi me-chanical deboner (Ikeuchi Tekkosho, Ltd., Japan) was washed twice in cold water (< 5°C) for 5 min, using a water/meat ratio of 3:1 for the first wash and ...
Journal of Agricultural and Food Chemistry, Aug 9, 2006
The effect of sonication during chitin extraction from freshwater prawn shells on yield, purity, ... more The effect of sonication during chitin extraction from freshwater prawn shells on yield, purity, and crystallinity of chitin was investigated. Dry prawn shells were suspended for 4 h in 0.25 M HCl at 40 degrees C while they were sonicated for 0, 1, and 4 h. Demineralized shells were lyophilized, resuspended in 0.25 M NaOH, and sonicated again for 0, 1, and 4 h for protein removal. The yield of chitin decreased from 8.28 to 5.02% for nonsonicated and sonicated samples, respectively, which was attributed to losses of depolymerized materials in the wash water. The application of ultrasound enhanced the removal of proteins. In nontreated shells, the amount of protein was 44.01% and was reduced to 12.55, 10.59, and 7.45% after 0, 1, and 4 h of sonication treatments. The glucosamine content slightly decreased with sonication probably because of losses due to depolymerization. The crystallinity indices of chitins decreased as the time of sonication increased. The degree of acetylation of chitins was unaffected by sonication, but the degree of acetylation of chitosans produced from sonicated chitin decreased from 70.0 to 68.7 and 61.4% for 1 and 4 h sonicated samples, respectively.
Food Research International, 2015
Journal of Food Science, May 1, 2004
Cod fillets were injected with brine, then immersed in brine with the same composition as used fo... more Cod fillets were injected with brine, then immersed in brine with the same composition as used for injection, and finally frozen in a plate freezer. The composition of the brine varied with groups, containing phosphates (3%), salt (5%), and/or proteins (10%), soy protein concentrate, or hydrolyzed cod proteins. The fillets were stored at -24°C for 3 mo and then thawed to evaluate the effects on yield after thawing and cooking, drip, water-holding capacity, pH, and chemical composition. Addition of proteins slightly increased the yield of thawed fillets, but salt and phosphates were more effective. Comparison of the different proteins showed that fish proteins were not as effective as soy proteins with respect to the physicochemical parameters evaluated with the exception of water-holding capacity. The use of both type of proteins resulted in a negative appearance of the fillets, such as discoloration and slimy surface.