• Bulletin of the Korean Chemical Society
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• v.3 no.2
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• pp.60-66
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• 1982

In relation to denaturation of proteins, thermally induced conformational change of poly(D-glutamic acid) was studied in the presence of poly(vinyl alcohol) at low pH, where poly(D-glutamic acid) undergoes a helix-to-${\beta}$ transition without any other polymer. In a dilute solution, poly(vinyl alcohol) enhanced the ${\alpah}-to-{\beta}_1$ transition of poly(D-glutamic acid) due to intermolecular interaction between the two polymers. On the other hand, this conformational change was interrupted to a large extent in a concentrated solution, due to the interpenetration of poly(vinyl alcohol) chain into poly(D-glutamic acid) chain which prevented the intramolecular association of poly(D-glutamic acid) chain. A conformational change from ${\beta}_1\;to\;{\beta}_2$ of poly(D-glutamic acid) was observed for the films obtained by casting during annealing the mixture solutions. The ${\beta}_2$ content in the cast film increased with increasing poly(vinyl alcohol) content in the mixture.

• BMB Reports
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• v.35 no.2
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• pp.155-164
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• 2002

The structural aspects of ervatamin B have been studied in different types of alcohol. This alcohol did not affect the structure or activity of ervatamin B under neutral conditions. At a low pH (3.0), different kinds of alcohol have different effects. Interestingly, at a certain concentration of non-fluorinated, aliphatic, monohydric alcohol, a conformational switch from the predominantly $\alpha$-helical to $\beta$-sheeted state is observed with a complete loss of tertiary structure and proteolytic activity. This is contrary to the observation that alcohol induces mostly the $\alpha$helical structure in proteins. The O-state of ervatamin B in 50% methanol at pH 3.0 has enhanced the stability towards GuHCl denaturation and shows a biphasic transition. This suggests the presence of two structural parts with different stabilities that unfold in steps. The thermal unfolding of ervatamin B in the O-state is also biphasic, which confirms the presence of two domains in the enzyme structure that unfold sequentially. The differential stabilization of the structural parts may also be a reflection of the differential stabilization of local conformations in methanol. Thermal unfolding of ervatamin B in the absence of alcohol is cooperative, both at neutral and low pH, and can be fitted to a two state model. However, at pH 2.0 the calorimetric profiles show two peaks, which indicates the presence of two structural domains in the enzyme with different thermal stabilities that are denatured more or less independently. With an increase in pH to 3.0 and 4.0, the shape of the DSC profiles change, and the two peaks converge to a predominant single peak. However, the ratio of van't Hoff enthalpy to calorimetric enthalpy is approximated to 2.0, indicating non-cooperativity in thermal unfolding.

• Korea-Australia Rheology Journal
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• v.19 no.1
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• pp.43-47
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• 2007

The polydiacethylene (PDA) is known to change its color by mechanical shear. The shear-induced color transition has been reported with elastomer or film type of PDA. In this paper, we newly investigated the transition with liposome type of PDAs in polymeric solutions. The liposomes were dispersed in Poly(vinyl alcohol) 2% + Sodium borate 1%, Poly(vinyl alcohol) 15% and Hyaluronic acid 1% (PVA/B, PVA, HA). The shear stress was continuously imposed to each solution by stress control type rheometer with coni-cylinder fixture. The degree of color transition was quantified with the characteristic absorbance peak at 540 nm (blue) and 640 nm (red). As a result, PDA liposome in PVA/B solution changed the color from blue to red upon increasing the magnitude of shear (from 0 to 100 Pa) and the duration of shear-imposed time (from 0 to 5400 sec). Meanwhile, PDA liposome in HA or PVA solution did not noticeably change the color, even though the low shear viscosities of the solutions were kept almost constant. This color transition of PDA liposome is expected to measure the magnitude of shear, and to distinguish different responses of polymeric solutions to the applied shear.

• BMB Reports
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• v.37 no.5
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• pp.586-596
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• 2004

The folding of ervatamin C was investigated in the presence of various fluorinated and non-fluorinated organic solvents. The differences in the unfolding of the protein in the presence of various organic solvents and the stabilities of O-states were interpreted. At pH 2.0, non-fluorinated alkyl alcohols induced a switch from the native $\alpha$-helix to a $\beta$-sheet, contrary to the $\beta$-sheet to $\alpha$-helix conversion observed for many proteins. The magnitude of ellipticity at 215 nm, used as a measure of $\beta$-content, was found to be dependent on the concentration of the alcohol. Under similar conditions of pH, fluorinated alcohol enhanced the intrinsic a-helicity of the protein molecule, whereas the addition of acetonitrile reduced the helical content. Ervatamin C exhibited high stability towards GuHCl induced unfolding in different O-states. Whereas the thermal unfolding of O-states was non-cooperative, contrary to the cooperativity seen in the absence of the organic solvents under similar conditions. Moreover, the differential scanning calorimetry endotherms of the protein acquired at pH 2.0 were deconvoluted into two distinct peaks, suggesting two cooperative transitions. With increase in pH, the shape of the thermogram changed markedly to exhibit a major and a minor transition. The appearance of two distinct peaks in the DSC together with the non-cooperative thermal transition of the protein in O-states indicates that the molecular structure of ervatamin C consists of two domains with different stabilities.

• Journal of Sericultural and Entomological Science
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• v.53 no.2
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• pp.118-123
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• 2015

The structural transition of silk protein has been induced by various method including alcohol treatment. To know the effect of alcohol concentration on silk beads conformation, silk beads were prepared in different alcohol concentration (100%, 70%, and 50%) and then examined the infrared spectra of silk beads. Silk beads prepared in 100% alcohol showed at $1265cm^{-1}$ attributed ${\beta}-sheet$ conformation and did not showed a characteristic absorption peak from model drug. However, silk beads in 70% and 50% alcohol showed some peaks originated from model drug including $2933cm^{-1}$, $1069cm^{-1}$, and $973cm^{-1}$. These results means that the micro-environment of silk beads was affected by alcohol concentration.

• Molecules and Cells
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• v.21 no.2
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• pp.229-236
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• 2006

Gaegurin 4 (GGN4), a novel peptide isolated from the skin of a Korean frog, Rana rugosa, has broad spectrum antimicrobial activity. A number of amphipathic peptides closely related to GGN4 undergo a coil to helix transition with concomitant oligomerization in lipid membranes or membrane-mimicking environments. Despite intensive study of their secondary structures, the oligomeric states of the peptides before and after the transition are not well understood. To clarify the structural basis of its antibiotic action, we used analytical ultracentrifugation to define the aggregation state of GGN4 in water, ethyl alcohol, and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). The maximum size of GGN4 in 15% HFIP corresponded to a decamer, whereas it was monomeric in buffer. The oligomeric transition is accompanied by a cooperative 9 nm blue-shift of maximum fluorescence emission and a large secondary structure change from an almost random coil to an ${\alpha}$-helical structure. GGN4 induces pores in lipid membranes and, using electrophysiological methods, we estimated the diameter of the pores to be exceed $7.3{\AA}$, which suggests that the minimal oligomer structure responsible is a pentamer.

• Journal of dental hygiene science
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• v.19 no.2
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• pp.141-146
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• 2019

Background: Oral cancer has a high incidence worldwide and has been closely associated with smoking, alcohol, and infection by the human papillomavirus. Metastasis is highly important for oral cancer survival. Lysophosphatidic acid (LPA) is a bioactive lipid mediator that promotes various cellular processes, including cell survival, proliferation, metastasis, and invasion. Signal transducer and activator of transcription (STATs) are transcription factors that mediate gene expression. Among the seven types of STATs in mammals, STAT3 is involved in invasion and metastasis of numerous tumors. However, little is known about the role of STAT3 in oral tumor invasion. In the present study, we hypothesized that STAT3 mediates LPA-induced oral cancer invasion. Methods: Immunoblotting was performed to analyze LPA-induced STAT3 activation. 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was performed to assess the survival rates of YD-10B cells. STAT3 levels in LPA-treated oral tumor cells were evaluated by performing in vitro invasion assay. Results: To the best of our knowledge, this is the first study to demonstrate that LPA enhances STAT3 phosphorylation in oral cancer. In addition, treatment with WP1066, a selective inhibitor of STAT3, at a concentration that does not cause severe reduction in cell viability, significantly attenuated LPA-induced YD-10B cancer cell invasion. Conclusion: The results suggested that LPA induces oral tumor cells with greater invasive potential via STAT3 activation. Our findings provided important insights into the mechanisms underlying mouth neoplasms.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.509-512
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• 2009

Powder diffraction patterns of the zeolite mesolite ($Na_{5.33}Ca_{5.33}Al_{16}Si_{24}O_{80}{\cdot}21.33H_2O$), with a natrolite framework topology were measured as a function of pressure up to 5.0 GPa using a diamond-anvil cell and a $200{\mu}m$-focused monochromatic synchrotron X-ray. Under the hydrostatic conditions mediated by pore-penetrating alcohol and water mixture, the elastic behavior of mesolite is characterized by continuous volume expansion between ca. 0.5 and 1.5 GPa, which results from expansion in the ab-plane and contraction along the c-axis. Subsequent to this anomalous behavior, changes in the powder diffraction patterns suggest possible reentrant order-disorder transition. The ordered layers of sodium- and calcium-containing channels in a 1:2 ratio along the b-axis attribute to the $3b_{natrolite}$ cell below 1.5 GPa. When the volume expansion is completed above 1.5 GPa, such characteristic ordering reflections disappear and the $b_{natrolite}$ cell persists with marginal volume contraction up to ca. 2.5 GPa. Further increase in pressure leads to progressive volume contraction and appears to generate another set of superlattice reflections in the $3c_{natrolite}$ cell. This suggests that mesolite in the pressure-induced hydration state experiences order-disorder-order transition involving the motions of sodium and calcium cations either through cross-channel diffusion or within the respective channels.