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Biomedical subjects

L A Preston

Publications and source records attributed to L A Preston.

6 recordsLinked to original sources
PubMed2001

Analysis and expression of algL, which encodes alginate lyase in Pseudomonas syringae Pv. syringae.

Pseudomonas syringae produces alginate, an exopolysaccharide that contributes to the virulence and epiphytic fitness of this phytopathogenic bacterium. P. syringae also produces the algL-encoded alginate lyase, which cleaves the alginate biopolymer via a beta-elimination reaction. The algL gene from P. syringae maps to a 1134 bp region within the alginate biosynthetic operon, and is similar to algL from Halomonas marina, P. aeruginosa, Azotobacter chroococcum, and A. vinelandii. algL from P. syringae was over expressed in Escherichia coli; two periplasmic forms of AlgL were overproduced (40 and 37 kDa). Both forms were enzymatically active and recognized by antibodies raised against AlgL from P. aeruginosa. Analysis of the regions flanking algL revealed significant homology to algX and algI, genes previously identified in the biosynthetic operon of other alginate-producing bacteria.

Amino Acid Sequence↗
PubMed2000

Characterization of alginate lyase from Pseudomonas syringae pv. syringae.

The gene encoding alginate lyase (algL) in Pseudomonas syringae pv. syringae was cloned, sequenced, and overexpressed in Escherichia coli. Alginate lyase activity was optimal when the pH was 7.0 and when assays were conducted at 42 degrees C in the presence of 0.2 M NaCl. In substrate specificity studies, AlgL from P. syringae showed a preference for deacetylated polymannuronic acid. Sequence alignment with other alginate lyases revealed conserved regions within AlgL likely to be important for the structure and/or function of the enzyme. Site-directed mutagenesis of histidine and tryptophan residues at positions 204 and 207, respectively, indicated that these amino acids are critical for lyase activity.

Cloning, Molecular↗
PubMed2000

ALGINATE LYASE: review of major sources and enzyme characteristics, structure-function analysis, biological roles, and applications.

Alginate lyases, characterized as either mannuronate (EC 4.2.2.3) or guluronate lyases (EC 4.2.2.11), catalyze the degradation of alginate, a complex copolymer of alpha-L-guluronate and its C5 epimer beta-D-mannuronate. Lyases have been isolated from a wide range of organisms, including algae, marine invertebrates, and marine and terrestrial microorganisms. This review catalogs the major characteristics of these lyases, the methods for analyzing these enzymes, as well as their biological roles. Analysis of primary sequence data identifies some markedly conserved motifs that should help elucidate functional domains. Information about the three-dimensional structure of a mannuronate lyase from Sphingomonas sp., combined with various mutagenesis studies, has identified residues that are important for catalytic activity in several lyases. Characterization of alginate lyases will enhance and expand the use of these enzymes to engineer novel alginate polymers for applications in various industrial, agricultural, and medical fields. In this review, we explore both past and present applications of this important enzyme and discuss its future prospects.

Alginates↗
PubMed1996

Individuality and relatedness of the self: an autophotographic study.

Using R. C. Ziller's (1990) method of autophotography, the authors studied the duality of relatedness and individuality. A total of 226 young adults used photos (and words) to portray "who they are". Photo essays were scored for objective codes (e.g., people touching) and subjectively rated for individuality (richness of self-depiction). As predicted, persons who emphasized their personal rather than social identity depicted greater individuality; relatedness was associated with social and collective identity. Other results replicated earlier gender differences in relatedness and associations of individuality and relatedness with the 5-factor model. In the 2nd wave of the sample, individuality was associated with higher ego development, maturity, and self-directed values; low individuality was associated with restrictive conformity and security values. The authors suggest that the combination of individuality and relatedness is optimal for human development.

Adult↗
PubMed1992

Reported head injury and sex differences in color naming, color matching, and digit-string matching.

It was hypothesized that the observed sex differences on three speeded tasks could be accounted for in terms of the greater incidence of head injury in men than in women. In two studies of 64 male and 66 female college students significant sex differences were found on digit-string matching and color-matching tasks. When the data from those 39 subjects with reported histories of head injury were eliminated from the analysis or head-injury reports were statistically controlled, significant sex differences remained. Digit-string matching times were significantly correlated with reported head injury in both studies, suggesting that this test is sensitive to residual effects of head injury.

Adult↗