• BMB Reports
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• v.44 no.10
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• pp.674-679
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• 2011

Bacillus sphaericus produces mosquito-larvicidal binary toxin composed of BinA and BinB. While BinB is expected to bind to a specific receptor on the cell membrane, BinA interacts to BinB or BinB receptor complex and translocates into the cytosol to exert its activity via unknown mechanism. To investigate functional roles of aromatic cluster in BinA, amino acids at positions Y213, Y214, Y215, W222 and W226 were substituted by leucine. All mutant proteins were highly produced and their secondary structures were not affected by these substitutions. All mutants are able to insert into lipid monolayers as observed by Langmuir-Blodgett trough and could permeabilize the liposomes in a similar manner as the wild type. However, mosquito-larvicidal activity was abolished for W222L and W226L mutants suggesting that tryptophan residues at both positions play an important role in the toxicity of BinA, possibly involved in the cytopathological process after toxin entry into the cells.

• BMB Reports
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• v.42 no.12
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• pp.769-775
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• 2009

Periplasmic glucans (PGs) are general constituents in the periplasmic space of Proteobacteria. PGs from bacterial strains are found in larger amounts during growth on medium with low osmolarity and thus are often been specified as osmoregulated periplasmic glucans (OPGs). Furthermore, they appear to play crucial roles in pathogenesis and symbiosis. PGs have been classified into four families based on the structural features of their backbones, and they can be modified by a variety of non-sugar substituents. It has also recently been confirmed that novel PGs with various degrees of polymerization (DPs) and/or different substituents are produced under different growth conditions among Proteobacteria. In addition to their biological functions as regulators of low osmolarity, PGs have a variety of physico-chemical properties due to their inherent three-dimensional structures, hydrogen-bonding and complex-forming abilities. Thus, much attention has recently been focused on their physico-chemical applications. In this review, we provide an updated classification of PGs, as well as a description of the occurrences of novel PGs with substituents under various bacterial growth environments, the genes involved in PG biosynthesis and the various physico-chemical properties of PGs.

• Journal of Biomedical Engineering Research
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• v.16 no.1
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• pp.9-16
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• 1995

Biodegradable poly (I ,4-butanediol succinate) (PBS) was synthesized from 1,4-butanediol and succinic anhydride. The glass transition temperature of poly (I, 4-butanediol succinate) was revealed at $73^{\circ}C$. The crystallization and cold crystallization of the polymers were investigated as a function of holding time in melt state, cooling rate. reheating, and molecular weight. Chain scission and/or cmsslinking did not occur in the melt state at var.ious holding times. Slower scanning rate can allow more times for nucleation, rearrangement, and packing of the polymer chain, so the onset temperature of crystallization from the melt was increased. PBS crystallized from the melt was found to have spherulitic structure. The degradation behavior of PBS was studied under basic conditions and with microorganisms using the modified ASTM method. In the basic solution. PBS lost up to 85% of its mass within two days. Based upon visual observation, the crystalline structure of films composed of larger molecular weight polymers retained their crystallinity longer than similar structures in low molecular weight samples.

• Asian-Australasian Journal of Animal Sciences
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• v.20 no.5
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• pp.802-810
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• 2007

Fibrobacter succinogenes, a Gram-negative, anaerobic ruminal bacterium is a major fibre digesting species in the rumen. It intensively degrades plant cell walls by an erosion type of mechanism, burrowing its way through the complex matrix of cellulose and hemicellulose with the release of digestible and undigested cell wall fragments. The enzymes involved in this process include a combination of glucanases, xylanases, arabinofuranosidase(s) and esterases. The genome of the bacterium has been sequenced and this has revealed in excess of 100 putative glycosyl hydrolase, pectate lyase and carbohydrate esterase genes, which is greater than the numbers reported present in other major cellulolytic organisms for which genomes have been sequenced. Modelling of the amino acid sequences of two glycanases, CedA and EGB, by reference to crystallized homologs has enabled prediction of the major features of their tertiary structures. Two dimensional gel electrophoresis in conjunction with mass spectroscopy has permitted the documentation of proteins over expressed in F. succinogenes grown on cellulose, and analysis of the cell surfaces of mutant strains unable to bind to cellulose has enabled the identification of candidate proteins with roles in adhesion to the plant cell wall substrate, the precursor to cellulose biodegradation.

• BMB Reports
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• v.49 no.8
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• pp.431-436
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• 2016

Human papillomavirus (HPV) is the major cause of cervical cancer, a deadly threat to millions of females. The early oncogene product (E7) of the high-risk HPV16 is the primary agent associated with HPV-related cervical cancers. In order to understand how E7 contributes to the transforming activity, we investigated the structural features of the flexible N-terminal region (46 residues) of E7 by carrying out N-15 heteronuclear NMR experiments and replica exchange molecular dynamics simulations. Several NMR parameters as well as simulation ensemble structures indicate that this intrinsically disordered region of E7 contains two transient (10-20% populated) helical pre-structured motifs that overlap with important target binding moieties such as an E2F-mimic motif and a pRb-binding LXCXE segment. Presence of such target-binding motifs in HPV16 E7 provides a reasonable explanation for its promiscuous target-binding behavior associated with its transforming activity.

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2005.11a
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• pp.40-64
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• 2005

Much biochemical information on peroxiredoxins (Prxs) has been reported but a genuine physiological function for these proteins has not been established. We show here that two cytosolic yeast Prxs, cPrxI and II, exist in a variety of forms that differ in their structure and molecular weight (MW) and that they can act both as a peroxidase and as a molecular chaperone. The peroxidase function predominates in the lower MW proteins, whereas the chaperone function is more significant in the higher MW complexes. Oxidative stress and heat shock exposure of yeasts causesthe protein structures of cPrxI and II to shift from low MW species to high MW complexes. This triggers a peroxidase-to-chaperone functional switch. These in vivo changes are primarily guided by the active peroxidase site residue, $Cys^{47}$, which serves as an efficient $'H_2O_2-sensor'$ in the cells. The chaperone function of the proteins enhances yeast resistance to heat shock.

• Journal of the Korean Applied Science and Technology
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• v.30 no.1
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• pp.96-115
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• 2013

This article describes the concept and the trend of antimicrobial coating agents, which will help to establish the direction of the research and development on antimicrobial coating agent. Antimicrobial agents are compounds that inhibit or kill microorganisms. They are classified into inorganic, metallic, low molecular weight organic, natural organic, and polymeric compounds. Antimicrobial coatings are applied to the surface of daily necessities, medical devices, industrial products, electrical appliances, fabrics, and interior building materials, etc. Conventional antibiotics penetrate microbes without damaging bacterial cell walls, leading to drug resistance which polymeric antimicrobials can prevent by disrupting cell walls. Most polymeric antimicrobials are focused on cationic polymers. Improvement in the selectivity and durability of antimicrobials and reduction of their toxicity will come true by more reasonable design of molecular structures and their combination in coating system.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.81-81
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• 2017

Nanotechnology is of great importance to molecular biology and medicine because life processes are maintained by the action of a series of molecular nanomachines in the cell machinery. Recent advances in nanoscale materials that possess emergent physical properties and molecular organization hold great promise to impact human health in the diagnostic and therapeutic arenas. In order to be effective, nanomaterials need to navigate the host biology and traffic to relevant biological structures, such as diseased or pathogenic cells. Moreover, nanoparticles intended for human administration must be designed to interact with, and ideally leverage, a living host environment. Inspired by nature, we use peptides to transfer biological trafficking properties to synthetic nanoparticles to achieve targeted delivery of payloads. In this talk, development of nanoscale materials will be presented with a particular focus on applications to three outstanding health problems: bacterial infection, cancer detection, and traumatic brain injury. A biodegradable nanoparticle carrying a peptide toxin trafficked to the bacterial surface has antimicrobial activity in a pneumonia model. Trafficking of a tumor-homing nanoprobes sensitively detects cancer via a high-contrast time-gated imaging system. A neuron-targeted nanoparticle carrying siRNA traffics to neuronal populations and silences genes in a model of traumatic brain injury. Unique combinations of material properties that can be achieved with nanomaterials provide new opportunities in translational nanomedicine. This framework for constructing nanomaterials that leverage bio-inspired molecules to traffic diagnostic and therapeutic payloads can contribute on better understanding of living systems to solve problems in human health.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2903-2908
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• 2010

Protein S-nitrosation is common in cells under nitrosative stress. In order to model proteins with S-nitrosocysteine (CysSNO) residues, we first developed an Amber force field for S-nitrosoethanethiol (EtSNO) and then transferred it to CysSNO. Partial atomic charges for EtSNO and CysSNO were obtained by a restrained electrostatic potential approach to be compatible with the Amber-99 force field. The force field parameters for bonds and angles in EtSNO were obtained from a generalized Amber force field (GAFF) by running the Antechamber module of the Amber software package. The GAFF parameters for the CC-SN and CS-NO dihedrals were not accurate and thus determined anew. The CC-SN and CS-NO torsional energy profiles of EtSNO were calculated quantum mechanically at the level of B3LYP/cc-pVTZ//HF/6-$31G^*$. Torsional force constants were obtained by fitting the theoretical torsional energies with those obtained from molecular mechanics energy minimization. These parameters for EtSNO reproduced, to a reasonable accuracy, the corresponding torsional energy profiles of the capped tripeptide ACE-CysSNO-NME as well as their structures obtained from quantum mechanical geometry optimization. A molecular dynamics simulation of myoglobin with a CysSNO residue produced a well-behaved trajectory demonstrating that the parameters may be used in modeling other S-nitrosated proteins.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.169-172
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• 2009

We developed ultra-accelerated quantum chemical molecular dynamics and characterization simulators for study and design of plasma display panel (PDP) related materials. By use of these simulators, realistic structure of PDP materials is drawn on the computer. Furthermore, based on the structures, various properties such as secondary electron emission coefficient are successfully evaluated. In this report, we will discuss the theoretical secondary electron emission coefficient for several protecting layer materials and the effect of surface structure on the properties based on the result of atomistic simulations.