• Korean Chemical Engineering Research
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• v.44 no.1
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• pp.92-96
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• 2006

Enzymes in organic media afford many advantages such as chiral synthesis and resolution, modification of fats and oils and production of biodegradable polymers. However, the nature of solvents influences the activity and stability of enzymes, and the presence of organic solvents always constitute a risk of enzyme inactivation. Heat-shock protein Hsp90, one of the molecular chaperone, was applied for understanding of enzyme inactivation and for increasing of enzyme stability in water-miscible organic solvent. Hsp90 showed stabilization effect on HRP in the 30％ of DMSO, in the 30％ and 50％ of dioxane. Hsp90 also showed reactivation effect on the inactivated HRP by water-miscible organic solvent such as dioxane and DMSO. In addition, structural analysis using fluorescence spectrophotometry and circular dichroism showed that exposure of HRP in water-miscible organic solvent caused appreciable conformational changes and enzyme inactivation, and the unfolded HRP by water-miscible organic solvent was refolded by Hsp90.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.3
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• pp.310-319
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• 2012

In order to investigate the biological effects of conformational changes in the folding state of bovine ${\alpha}$-lactalbumin (${\alpha}$-La), the protein was prepared and classified as apo form, microbial transglutaminase (MTGase) added form, or bovine ${\alpha}$-La made lethal to tumor cell (BAMLET) form. Apo ${\alpha}$-La form showed weaker cancer cell inhibitory activity (apoptosis) than native ${\alpha}$-La, which suggests that the metal ion-like $Ca^{2+}$ had a positive effect, whereas BAMLET form showed strong cancer cell apoptotic activity. The BAMLET form seemed to be a molten globule structure that increased hydrophobicity. MTGase added to apo ${\alpha}$-La polymer showed similar anti-cancer activity as native ${\alpha}$-La, and it was well hydrolyzed by digestive enzymes. NMR results showed that BAMLET interacted with oleic acid and produced a complex.

• Journal of Microbiology and Biotechnology
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• v.25 no.1
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• pp.33-43
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• 2015

GAM-1 and GAM-2, two themostable glucoamylases from Aspergillus niger B-30, possess different molecular masses, glycosylation, and thermal stability. In the present study, the effects of additives on the thermal inactivation of GAM-1 and GAM-2 were investigated. The half-lives of GAM-1 and GAM-2 at 70℃ were 45 and 216 min, respectively. Data obtained from fluorescence spectroscopy, circular dichroism spectroscopy, UV absorption spectroscopy, and dynamic light scattering demonstrated that during the thermal inactivation progress, combined with the loss of the helical structure and a majority of the tertiary structure, tryptophan residues were partially exposed and further led to glucoamylases aggregating. The thermal stability of GAM-1 and GAM-2 was largely improved in the presence of sorbitol and trehalose. Results from spectroscopy and Native-PAGE confirmed that sorbitol and trehalose maintained the native state of glucoamylases and prevented their thermal aggregation. The loss of hydrophobic bonding and helical structure was responsible for the decrease of glucoamylase activity. Additionally, sorbitol and trehalose significantly increased the substrate affinity and catalytic efficiency of the two glucoamylases. Our results display an insight into the thermal inactivation of glucoamylases and provide an important base for industrial applications of the thermally stable glucoamylases.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2000.11a
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• pp.91-97
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• 2000

The conventional model did not take momentum conservation into consideration when the electron absorbs and emits the photons. II-ray provides momentum conservations on any directions of the entering photons, and also the electrons have radial momentum conservations and fully elastic bouncing between two atoms, in the new atom model. Conventional atom model must be criticized on the following four points. (1) Natural motions between positive and negative entities are not circular motions but linear going and returning ones, for examples sexual motion, tidal motion, day and night etc. Because the radius of hydrogen atom's electron orbit is the order of 10$^{-11}$ m and the radia of the nucleons in the nucleus are the order of 10$^{-l4}$m and then the converging n-gamma rays to the nucleus have so great circular momentum, the electron can not have a circular motion. We can say without doubt that any elementary mass particle can have only linear motion because of the n-rays' hindrances, near the nucleus. (2) Potential energy generation was neglected when electron changes its orbit from outer one to inner one. The h v is the kinetic energy of the photo-electron. The total energy difference between orbits comprises kinetic and potential energies. (3) The structure of the space must be taken into consideration because the properties of the electron do not change during the transition from outer orbit to inner one even though it produces photon. (4) Total energy conservation law applies to the energy flow between mind and matter because we daily experiences a interconnection between mind and body. An understanding of the mechanisms responsible for the control of normal proliferation and differentiation of the various cell types which make up the human body will undoubtedly allow a greater insight into the abnormal growth of cells, A large body of biochemical evidence was eventually used to generate a receptor model with an external ligand binding domain linked through a single trans-membrane domain to the cytoplasmic tyrosine kinase and autophosphory-lation domains. The ligand induced conformational change in the external domain generates either a push-pull or rotational signal which is transduced from the outside to the inside of cell.l.ell.

• Molecules and Cells
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• v.28 no.1
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• pp.25-30
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• 2009

${\beta}$-Arrestins turn off G protein-mediated signals and initiate distinct G protein-independent signaling pathways. We previously demonstrated that angiotensin $AT_1$ receptorbound ${\beta}$-arrestin 1 is cleaved after $Phe^{388}$ upon angiotensin II stimulation. The mechanism and signaling pathway of angiotensin II-induced ${\beta}$-arrestin cleavage remain largely unknown. Here, we show that protein Tyr phosphatase activity is involved in the regulation of ${\beta}$-arrestin 1 cleavage. Tagging of green fluorescent protein (GFP) either to the N-terminus or C-terminus of ${\beta}$-arrestin 1 induced conformational changes and the cleavage of ${\beta}$-arrestin 1 without angiotensin $AT_1$ receptor activation. Orthovanadate and molybdate, inhibitors of protein Tyr phosphatase, attenuated the cleavage of C-terminal GFP-tagged ${\beta}$-arrestin 1 in vitro. The inhibitory effects of okadaic acid and pyrophosphate, which are inhibitors of protein Ser/Thr phosphatase, were less than those of protein Tyr phosphatase inhibitors. Cell-permeable pervanadate inhibited angiotensin II-induced cleavage of ${\beta}$-arrestin 1 in COS-1 cells. Our findings suggest that Tyr phosphorylation signaling is involved in the regulation of angiotensin II-induced ${\beta}$-arrestin cleavage.

• Food Science of Animal Resources
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• v.32 no.5
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• pp.627-634
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• 2012

This study was carried out to investigate the physical and thermal properties of ${\kappa}$-carrageenan (${\kappa}$-car) gel added whey protein isolate (WPI) as a cryoprotectant. The concentration of ${\kappa}$-carrageenan was fixed at 0.2 wt%. The mean ice crystal size of the WPI/${\kappa}$-car was decreased according to increasing whey protein isolate concentration. The temperature of gel-sol (Tg-s) and sol-gel (Ts-g) transition of WPI/${\kappa}$-car maxtrix was represented in the order of 3.0, 0.2, 5.0 and 1.0 wt%. In addition, the transition temperature of gel-sol of WPI in sucrose solution were showed in order of 1.0, 5.0, 0.2 and 3.0 wt% depending on whey protein isolate concentration. The shape of ice crystal was divided largely into two types, round and rectangular form. 1.0 wt% WPI/${\kappa}$-car matrix at pH 7 and 9 showed minute and rectangular formation of ice crystals and whey protein isolate in sucrose solution at a concentration of 1.0 wt% WPI/${\kappa}$-car matrix at pH 3 and 5 showed relatively large size and round ice crystals. The ice recrystallization characteristics and cryprotective effect of ${\kappa}$-carrageenan changed through the addition of different concentrations of whey protein isolate. It seems that the conformational changes induced interactions between whey protein isolate and ${\kappa}$-carrageenan affected ice recrystallization.

• Journal of the Korean Chemical Society
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• v.36 no.2
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• pp.324-328
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• 1992

The $^1H$ NMR chemical shifts and coupling constants for ${\alpha}$-, permethyl-${\alpha}$-, ${\beta}$-and permethyl-${\beta}$-cyclodextrins in neutral aqueous media were assigned based on the 470MHz spectra. In order to obtain accurate chemical shifts and coupling constants the experimental spectra were analyzed with the Raccoon spin simulation program. The rotamer distribution around the$C_{5-}C_6$ bond of the cyclodextrins evaluated from the coupling constants of $J_{56a}$ and $J_{56b}$. In our calculation of the ${\alpha}$-, and ${\beta}$-cycliodextrin showed that gg conformers were most favorable form and tg conformers were least favorable form. It is very interesting to note the changes in $J_{56a}$, $J_{56b}$ coupling constants of permethylated ${\alpha}$- and ${\beta}$-cyclodextrins from unmodified one. The gg conformers were more increased than unmodified one and instead of tg conformers gt conformers were least favorable one upon methylation.

• Journal of Microbiology and Biotechnology
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• v.26 no.11
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• pp.1845-1854
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• 2016

The transglycosylation activity of amylosucrase (ASase) has received significant attention owing to its use of an inexpensive donor, sucrose, and broad acceptor specificity, including glycone and aglycone compounds. The transglycosylation reaction of recombinant ASase from Deinococcus radiopugnans (DRpAS) was investigated using various phenolic compounds, and quercetin-3-O-rutinoside (rutin) was found to be the most suitable acceptor molecule used by DRpAS. Two amino acid residues in DRpAS variants (DRpAS Q299K and DRpAS Q299R), assumed to be involved in acceptor binding, were constructed by site-directed mutagenesis. Intriguingly, DRpAS Q299K and DRpAS Q299R produced 10-fold and 4-fold higher levels of rutin transglycosylation product than did the wild-type (WT) DRpAS, respectively. According to in silico molecular docking analysis, the lysine residue at position 299 in the mutants enables rutin to more easily position inside the active pocket of the mutant enzyme than in that of the WT, due to conformational changes in loop 4.

• BMB Reports
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• v.35 no.2
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• pp.143-154
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• 2002

The structural and functional aspects of ervatamin B were studied in solution. Ervatamin B belongs to the $\alpha+\beta$ class of proteins. The intrinsic fluorescence emission maximum of the enzyme was at 350 nm under neutral conditions, and at 355 nm under denaturing conditions. Between pH 1.0-2.5 the enzyme exists in a partially unfolded state with minimum or no tertiary structure, and no proteolytic activity. At still lower pH, the enzyme regains substantial secondary structure, which is predominantly $\beta$-sheet conformation and shows a strong binding to 8-anilino-1-napthalene-sulfonic acid (ANS). In the presence of salt, the enzyme attains a similar state directly from the native state. Under neutral conditions, the enzyme was stable in urea, while the guanidine hydrochloride (GuHCl) induced equilibrium unfolding was cooperative. The GuHCl induced unfolding transition curves at pH 3.0 and 4.0 were non-coincidental, indicating the presence of intermediates in the unfolding pathway. This was substantiated by strong ANS binding that was observed at low concentrations of GuHCl at both pH 3.0 and 4.0. The urea induced transition curves at pH 3.0 were, however, coincidental, but non-cooperative. This indicates that the different structural units of the enzyme unfold in steps through intermediates. This observation is further supported by two emission maxima in ANS binding assay during urea denaturation. Hence, denaturant induced equilibrium unfolding pathway of ervatamin B, which differs from the acid induced unfolding pathway, is not a simple two-state transition but involves intermediates which probably accumulate at different stages of protein folding and hence adds a new dimension to the unfolding pathway of plant proteases of the papain superfamily.

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.475-481
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• 2013

By using ionic liquid 1-hexylpyridinium hexafluorophosphate ($HPPF_6$) based carbon ionic liquid electrode (CILE) as the substrate electrode, a $CoMoO_4$ nanorods and myoglobin (Mb) composite was casted on the surface of CILE with chitosan (CTS) as the film forming material to obtain the modified electrode (CTS/$CoMoO_4$-Mb/CILE). Spectroscopic results indicated that Mb retained its native structures without any conformational changes after mixed with $CoMoO_4$ nanorods and CTS. Electrochemical behaviors of Mb on the electrode were carefully investigated by cyclic voltammetry with a pair of well-defined redox peaks from the heme Fe(III)/Fe(II) redox center of Mb appeared, which indicated that direct electron transfer between Mb and CILE was realized. Electrochemical parameters such as the electron transfer number (n), charge transfer coefficient (${\alpha}$) and electron transfer rate constant ($k_s$) were estimated by cyclic voltammetry with the results as 1.09, 0.53 and 1.16 $s^{-1}$, respectively. The Mb modified electrode showed good electrocatalytic ability toward the reduction of trichloroacetic acid in the concentration range from 0.1 to 32.0 mmol $L^{-1}$ with the detection limit as 0.036 mmol $L^{-1}$ ($3{\sigma}$), and the reduction of $H_2O_2$ in the concentration range from 0.12 to 397.0 ${\mu}mol\;L^{-1}$ with the detection limit as 0.0426 ${\mu}mol\;L^{-1}$ ($3{\sigma}$).