• Journal of the Korean Magnetic Resonance Society
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• v.7 no.1
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• pp.37-45
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• 2003

Human CD99 is a ubiquitous 32-kDa transmembrane protein encoded by mic2 gene. Recently it has been reported that expression of a splice variant of CD99 transmembrane protein (Type I and Type II) increases invasive ability of human breast cancer cells. To understand structural basis for cellular functions of CD99 Type II, we have initiated studies on hCD99$\^$TMcytoI/ using circular dichroism (CD) and multi-dimensional NMR spectroscopy. CD spectrum of hCD99$\^$TMytoI/ in the presence of 200mM DPC and CHAPS displayed an existence ${\alpha}$-helical conformation, showing that it could form an ${\alpha}$-helix under membrane environments. In addition, we have found that the cytoplasmic domain of CD99 would form symmetric dimmer in the presence of transmembrane domain. Although it has been rarely figured out the correlation between structure and functional mechanism of hCD99$\^$TMcytoI/, the dimerization or oligomerization would play an important role in its biological function.

• BMB Reports
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• v.47 no.5
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• pp.256-261
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• 2014

To investigate the function of N-glycosylation of Cel5A (endoglucanase II) from Hypocrea jecorina, two N-glycosylation site deletion Cel5A mutants (rN124D and rN124H) were expressed in Saccharomyces cerevisiae. The weights of these recombinant mutants were 54 kDa, which were lower than that of rCel5A. This result was expected to be attributed to deglycosylation. The enzyme activity of rN124H was greatly reduced to 60.6% compared with rCel5A, whereas rN124D showed slightly lower activity (10%) than that of rCel5A. rN124D and rN124H showed different thermal stabilities compared with the glycosylated rCel5A, especially at lower pH value. Thermal stabilities were reduced and improved for rN124D and rN124H, respectively. Circular dichroism spectroscopy showed that the modification of secondary structure by mutation may be the reason for the change in enzymatic activity and thermal stability.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3521-3524
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• 2010

MTH1880 is a hypothetical protein derived from Methanobacterium thermoautotrophicum, thermophilic methanogen. The solution structure determined by NMR spectroscopy showed that it has a novel $\alpha+\beta$-fold with a highly acidic ligand binding pocket. Since MTH1880 maintains its ultra-stable structural characteristics at both high temperature and pressure, it has been considered as an excellent model for studying protein folding. To initiate the structural and folding study of MTH1880 in proving its unusual stability, we performed the site directed mutagenesis and biochemical analysis of MTH1880 mutants. Data from circular dichroism and NMR spectroscopy suggest that the point mutations perturbed the structural stability of protein even though the secondary structure is retained. This study will provide the useful information in understanding the role of participating residues during folding-unfolding process and our result will be used in designing further folding experiments for hyper-thermopile proteins like MTH1880.

• Macromolecular Research
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• v.11 no.1
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• pp.2-8
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• 2003

The self-assembly of polymers can lead to supramolecular systems and is related to the their functions of material and life sciences. In this article, self-assembly of Langmuir-Blodgett (LB) films, polymer micelles, and polymeric nanoparticles, and their biomedical applications are described. LB surfaces with a well-ordered and layered structure adhered more cells including platelet, hepatocyte, and fibroblast than the cast surfaces with microphase-separated domains. Extensive morphologic changes were observed in LB surface-adhered cells compared to the cast films. Amphiphilic block copolymers, consisting of poly(${\gamma}$-benzyl L-glutamate) (PBLG) as the hydrophobic part and poly(ethylene oxide) (PEO) [or poly(N-isopropylacrylamide) (PNIPAAm)] as the hydrophilic one, can self-assemble in water to form nanoparticles presumed to be composed of the hydrophilic shell and hydrophobic core. The release characteristics of hydrophobic drugs from these polymeric nanoparticles were dependent on the drug loading contents and chain length of the hydrophobic part of the copolymers. Achiral hydrophobic merocyanine dyes (MDs) were self-assembled in copolymeric nanoparticles, which provided a chiral microenvironment as red-shifted aggregates, and the circular dichroism (CD) of MD was induced in the self-assembled copolymeric nanoparticles.

• Journal of the Korean Magnetic Resonance Society
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• v.13 no.2
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• pp.126-134
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• 2009

UBLCP1 is composed of Ubiquitin Like domain and RNA Polymerase II Phosphatase I domain. Phosphatase domain (25.9KDa) has been cloned into the E.coli using pET32a vector with TEV protease cleavage site and successfully purified as a monomer using affinity chromatography and histidine tag was cleaved with TEV protease for structural studies. Our results indicated that the Phosphatase domain showed well-defined folded structure based on data from one-dimensional and two-dimensional NMR spectroscopy. Data form circular dichroism also suggested that Phosphatase domain consisted of both ${\alpha}$ -helix and ${\beta}$ -sheet. This information will be used for detailed structural study of UBLCP1.

• Bulletin of the Korean Chemical Society
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• v.19 no.1
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• pp.57-62
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• 1998

We have synthesized a 17-residue peptide with the amino acid sequence RQMKEDAKGKSEEELAD corresponding to residues 84-100 of chicken skeletal troponin C. This stretch of the protein sequence is in the middle one-third of the 32-residue 9-turn α-helix that connects the two globular domains of the dumbell-shaped molecule and includes the D/E linker helix. We describe here the solution conformation of the helix linker as studied by circular dichroism (CD) and two-dimensional nuclear magnetic resonance (2-D NMR) spectroscopy. The NOE connectivities together with the vicinal $^3J_{N{\alpha}}$ coupling constants suggest that the peptide exists in a fast conformational equilibrium among several secondary structure: a nascent helix near the N-terminus, a helix, and a substational population of extended and random coil forms. In addition, two interresidue α-α NOEs are observed suggesting a bent structure with a bend that includes the single glycine in position 92. These results are consistent with the ideas that in neutral solution the D/E linker region of the central helix in troponin C can adopt a helical conformation and the central helix may have a segmental flexibility around Gly 92.

• Bulletin of the Korean Chemical Society
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• v.21 no.11
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• pp.1119-1124
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• 2000

$\beta-Cyclodextrin$ derivatives connected with diaza-18-crown-6 through flexible bridges (R) at the secondary face 1a-c (1a: R = $-(CH_2)4-;$ 1b: R = $-CH_2CH_2OCH_2CH2-;$ 1c: R = $-(CH_2)8-)$ have been prepared. The associa tion constants of 1 with (2-naphthoxy)alkylammonium ions (2a: alkyl = butyl; 2b: alkyl = octyl) were determined by induced circular dichroism (ICD) spectroscopy and it was found that the derivatization of $\beta-CD$ with the diazacrown resulted in enhanced binding with 2, compared to the native $\beta-CD.$ ICD Characteristics of the host-guest complexes indicate that a part of the alkylammonium moiety of 2 is protruded from the secondary side of the $\beta-CD$ cavity, and the guest molecules 2a and 2b move to the secondary and primary side, respectively, to make the binding of the ammonium group with the diaza-18-crown-6 moiety more feasible. The energy accompanied by the relocation of the guest molecules inside $\beta-CD$ moiety is compensated by the interaction energy between the ammonium ion and diazacrown ether.

• Bulletin of the Korean Chemical Society
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• v.28 no.2
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• pp.263-270
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• 2007

New mono- and bis-Cu(II)-triazacyclononane(tacn) complex that conjugated with 9-aminoacridine were synthesized, and their binding modes and DNA cleavage activity were investigated in this study. When the classic intercalator, 9-aminoacridine, was conjugated to mono- and bis-Cu(II)-tacn complexes, a significant red-shift and hypochromism in absorption spectrum was apparent in the acridine absorption region upon binding to DNA. Furthermore, the magnitude of the negative reduced linear dichroism signal in the substrate absorption region appeared to be larger than that in the DNA absorption region. These spectral observations indicated that the acridine moiety intercalated when the Cu(II)-tacn complex was conjugated. In contrast, from a close analysis of the circular and linear dichroism spectrum, the aminoacridine-free bis-Cu(II)-tacn complex was concluded to bind at the phosphate groups of DNA. The 9-aminoacridine-free-bis-Cu(II)-tacn complex produces the nicked and linear DNA. On the other hand, 9-aminoacridine conjugated mono-and bis-Cu(II)-tacn complexes showed unspecific binding with negligible DNA cleavage.

• Bulletin of the Korean Chemical Society
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• v.17 no.4
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• pp.358-362
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• 1996

The ionic strength dependent binding mode of 9-aminoacridine (9AA), a well-known DNA intercalator, to DNA is studied by flow linear dichroism, circular dichroism, fluorescence techniques and equilibrium dialysis. The DNA-bound 9AA exhibits spectral properties corresponding to the intercalative binding mode disregarding the salt concentrations; the angle between the long-axis transition moment of the 9AA molecule and DNA helix axis is calculated to be about 65°, indicating a significant deviation from the classical intercalation. At low salt concentrations, however, upwards bending curve in Stern-Volmer plot is observed (where 9AA is a fluorophore and DNA a quencher), indicating the coexistence of both static and dynamic quenching mechanisms or the existence of an additional binding site.

• Korean Journal of Food Science and Technology
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• v.21 no.5
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• pp.714-720
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• 1989

Effects of acetylation on conformational changes of glycinin was studied using solvent perturbation, second derivative spectroscopy, near uv circular dichroism spectra and viscosity. Glycinin with purity of more than 93% was used for the experiment. Modification was carried out with acetic anhydride and glycinin with lysine residue modification of 0%, 28%, 65%, 85%, and 95% were used for the experiment. The result of solvent perturbation using some selected perturbants, such as glycerol, ethylene glycol, and dimethyl sulfoxide revealed that acetylation has caused increase In solvent accessibility of tyrosine residues from less than 40% in native protein to more than 70% for 95% acetylated glycinin. This was confirmed by second derivative spectroscopy. Near ultraviolet circular dichroism revealed that the spectra of native and acetylated glycinin were almost identical differing only in intensity and no other useful information could be derived from it. However, in the case of 95% acetylated glycinin the influence of tryptophan on the spectrum was more pronounced Specific viscosity of glycinin also increased by modification, the extent of which depended upon the degree of acetylation. These results supported that acetylation had caused globular conformation of glycinin to be expanded and denatured.