Biomedical subjects

Hye Yoon Park

Publications and source records attributed to Hye Yoon Park.

6 recordsLinked to original sources

PubMed2006

Achieving uniform mixing in a microfluidic device: hydrodynamic focusing prior to mixing.

We describe a microfluidic mixer that is well-suited for kinetic studies of macromolecular conformational change under a broad range of experimental conditions. The mixer exploits hydrodynamic focusing to create a thin jet containing the macromolecules of interest. Kinetic reactions are triggered by molecular diffusion into the jet from adjacent flow layers. The ultimate time resolution of these devices can be restricted by premature contact between co-flowing solutions during the focusing process. Here, we describe the design and characterization of a mixer in which hydrodynamic focusing is decoupled from the diffusion of reactants, so that the focusing region is free from undesirable contact between the reactants. Uniform mixing on the microsecond time scale is demonstrated using a device fabricated by imprinting optical-grade plastic. Device characterization is carried out using fluorescence correlation spectroscopy (FCS) and two-photon microscopy to measure flow speeds and to quantify diffusive mixing by monitoring the collisional fluorescence quenching, respectively. Criteria for achieving microsecond time resolution are described and modeled.

Microfluidics↗

PubMed2006

Measuring inter-DNA potentials in solution.

Interactions between short strands of DNA can be tuned from repulsive to attractive by varying solution conditions and have been quantified using small angle x-ray scattering techniques. The effective DNA interaction charge was extracted by fitting the scattering profiles with the generalized one-component method and inter-DNA Yukawa pair potentials. A significant charge is measured at low to moderate monovalent counterion concentrations, resulting in strong inter-DNA repulsion. The charge and repulsion diminish rapidly upon the addition of divalent counterions. An intriguing short range attraction is observed at surprisingly low divalent cation concentrations, approximately 16 mM Mg2+. Quantitative measurements of inter-DNA potentials are essential for improving models of fundamental interactions in biological systems.

DNA, Single-Stranded↗

PubMed2006

Microbacterium paludicola sp. nov., a novel xylanolytic bacterium isolated from swamp forest.

A xylanolytic bacterium, US15T, was isolated from swamp forest soil in Ulsan, Korea. The cells of the novel strain were Gram-positive, non-motile, short-rod-shaped and showed chemotaxonomic properties that were consistent with its classification in the genus Microbacterium. Chemotaxonomic results showed MK-12 and MK-11 as major menaquinones, predominating iso- and anteiso-branched cellular fatty acids, glucose, galactose and mannose as cell-wall sugars, peptidoglycan-type B2beta with glycolyl residues and a DNA G + C content of 66.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequencing showed that strain US15T was closely related to Microbacterium arborescens IFO 3750T, Microbacterium imperiale IFO 12610T and Microbacterium ulmi LMG 20991T (96.9, 96.8 and 96.2 % similarities, respectively), and formed a separate lineage within the genus Microbacterium. Combined genotypic and phenotypic data showed that strain US15T (= DSM 16915T= KCTC 19080T) merits recognition as the type strain of a novel species within the genus Microbacterium, for which the name Microbacterium paludicola sp. nov. is proposed.

Actinomycetales↗

PubMed2005

Concordant exploration of the kinetics of RNA folding from global and local perspectives.

Time-resolved small-angle X-ray scattering (SAXS) with millisecond time-resolution reveals two discrete phases of global compaction upon Mg2+-mediated folding of the Tetrahymena thermophila ribozyme. Electrostatic relaxation of the RNA occurs rapidly and dominates the first phase of compaction during which the observed radius of gyration (R(g)) decreases from 75 angstroms to 55 angstroms. A further decrease in R(g) to 45 angstroms occurs in a well-defined second phase. An analysis of mutant ribozymes shows that the latter phase depends upon the formation of long-range tertiary contacts within the P4-P6 domain of the ribozyme; disruption of the three remaining long-range contacts linking the peripheral helices has no effect on the 55-45 angstroms compaction transition. A better understanding of the role of specific tertiary contacts in compaction was obtained by concordant time-resolved hydroxyl radical (OH) analyses that report local changes in the solvent accessibility of the RNA backbone. Comparison of the global and local measures of folding shows that formation of a subset of native tertiary contacts (i.e. those defining the ribozyme core) can occur within a highly compact ensemble whose R(g) is close to that of the fully folded ribozyme. Analyses of additional ribozyme mutants and reaction conditions establish the generality of the rapid formation of a partially collapsed state with little to no detectable tertiary structure. These studies directly link global RNA compaction with formation of tertiary structure as the molecule acquires its biologically active structure, and underscore the strong dependence on salt of both local and global measures of folding kinetics.

Animals↗

PubMed2005

Transfer of Chryseobacterium meningosepticum and Chryseobacterium miricola to Elizabethkingia gen. nov. as Elizabethkingia meningoseptica comb. nov. and Elizabethkingia miricola comb. nov.

The taxonomic positions of six strains (including the type strain) of Chryseobacterium meningosepticum (King 1959) Vandamme et al. 1994 and the type strain of Chryseobacterium miricola Li et al. 2004 were re-evaluated by using a polyphasic taxonomic approach. Phylogenetic analysis, based on 16S rRNA gene sequencing, showed that the strains represent a separate lineage from the type strains of the Chryseobacterium-Bergeyella-Riemerella branch within the family Flavobacteriaceae (90.7-93.9 % similarities), which was supported by phenotypic differences. Combined phylogenetic and phenotypic data showed that C. meningosepticum and C. miricola should be transferred to a new genus, Elizabethkingia gen. nov., with the names Elizabethkingia meningoseptica comb. nov. (type strain, ATCC 13253(T) = NCTC 10016(T) = LMG 12279(T) = CCUG 214(T)) and Elizabethkingia miricola comb. nov. (type strain, DSM 14571(T) = JCM 11413(T) = GTC 862(T)) proposed.

Bacterial Typing Techniques↗

PubMed2005

Microbacterium xylanilyticum sp. nov., a xylan-degrading bacterium isolated from a biofilm.

A novel xylan-degrading bacterium, S3-E(T), was isolated from the biofilm of a membrane bioreactor. The cells of this strain were Gram-positive, non-motile, non-spore-forming rods, produced primary branches and formed yellow colonies on nutrient agar. The strain had chemotaxonomic markers that were consistent with classification in the genus Microbacterium, i.e. MK-12, MK-11 and MK-13 as the major menaquinones, predominant iso- and anteiso-branched cellular fatty acids, glucose and galactose as the cell-wall sugars, peptidoglycan-type B2beta with glycolyl residues and a DNA G+C content of 69.7 mol%. Phylogenetic analysis, based on 16S rRNA gene sequencing, showed that strain S3-E(T) is most similar to Microbacterium hominis IFO 15708(T) and Microbacterium foliorum DSM 12966(T) (97.6 and 97.4% sequence similarity, respectively), and that it forms a separate lineage with M. hominis in the genus Microbacterium. DNA-DNA hybridization results and phenotypic properties showed that strain S3-E(T) could be distinguished from all known Microbacterium species and represented a novel species, for which the name Microbacterium xylanilyticum sp. nov. is proposed; the type strain is S3-E(T) (=DSM 16914(T)=KCTC 19079(T)).

Actinomycetales↗