• Preventive Nutrition and Food Science
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• 제2권4호
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• pp.281-284
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• 1997

Heat-induced gelation is an important functional property of whey proteins. Preheating of calcium reduced whey was reported to increase gel strength. 5% whey-protein solutions were preheated at pH7 and at various temperatures(60~8$0^{\circ}C$) for 15 minutes. The amount of soluble aggregates and denaturation enthalpy of preheated whey proteins were measured. Preheating temperature was negatively correlated with denaturation enthalpy($R^2$=0.857, P=0.08) and positive with the amount of soluble aggregates($R^2$=0.921, P=0.002). Denaturation enthalpy was negatively correlated with gel strength($R^2$=0.93, P=0.002). Soluble aggregates and gel strength were positively correlated($R^2$=0.972, P=0.0003). The formation of three dimensional gel network requires controlled protein denaturation and aggregation. Since preheating leads to the partial denaturation of proteins and the formation of soluble aggregates, preheated whey proteins have a higher gel strength than non-preheated one.

• BMB Reports
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• 제35권5호
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• pp.472-475
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• 2002

Phaseolus vulgaris phytohemagglutinin L is a homotetrameric-leucoagglutinating seed lectin. Its three-dimensional structure shows similarity with other members of the legume lectin family. The tetrameric form of this lectin is pH dependent. Gel filtration results showed that the protein exists in its dimeric state at pH 2.5 and as a tetramer at pH 7.2. Contrary to earlier reports on legume lectins that possess canonical dimers, thermal denaturation studies show that the refolding of phytohemagglutinin L at neutral pH is irreversible. Differential scanning calorimetry (DSC) was used to study the denaturation of this lectin as a function of pH that ranged from 2.0 to 3.0. The lectin was found to be extremely thermostable with a transition temperature around $82^{\circ}C$ and above $100^{\circ}C$ at pH 2.5 and 7.2, respectively. The ratio of calorimetric to vant Hoff enthalpy could not be calculated because of its irreversible-folding behavior. However, from the DSC data, it was discovered that the protein remains in its compact-folded state, even at pH 2.3, with the onset of denaturation occurring at $60^{\circ}C$.

• 한국축산식품학회:학술대회논문집
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• 한국축산식품학회 2004년도 정기총회 및 제33차 춘계 학술대회
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• pp.198-201
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• 2004

To investigate hydrostatic pressure (HP) effect on myofibrillar protein (Mf) extracted from bovine Semitendinosus muscle, Ca- and Mg-ATPase activities to evaluate denaturation of myosin and actin, and soluble protein contents were observed. In Mf treated with 100 MPa for 5 min was not observed denaturation of myosin and actin. In Mf treated with 200 MPa for 5 min, denaturation of myosin and actin were observed but inactivation rate was low (0.0136 $min^{-1}$). Inactivation rate of myosin and actin was dramatically increased above 300 MPa treatment. However denaturation of myosin and actin was not that critical with duration time. By increasing pressure size, the amount of myosin and actin in soluble protein eluted in 20 mM potassium phosphate buffer (pH 7.0) containing 0.6 M NaCl were decreased. SDS-PAGE of soluble protein released from Mf suspension in 0.1 M NaCl buffer (pH 7.0) showed that low molecular weight proteins (15${\sim}$36 KDa) were released by HP treatment above 200 MPa. From the results, denaturation of myosin and actin, and release of light molecule proteins of Mf were observed by HP treatment over 200 MPa.

• 대한화학회지
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• 제28권1호
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• pp.14-19
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• 1984

메트미오글로빈의 압력에 의한 변성의 $H_2O$와 $D_2O$에서의 차이를 pH 5.7과 pH 7.0에서 연구하였다. 메트미오글로빈은 $D_2O$에서 $H_2O$보다 더 작은 압력에서 변성하였다. 그 차이가 pH 5.7에서가 pH 7에서 보다 더 컸다. $H_2O$와 $D_2O$에서 이 안정도의 차이가 단백질에 대한 $H^+$와 $D^+$의 결합에 차이가 있기 때문이며 또한, 수소가 중수소로 바뀜에 따르는 구조 변화 때문인 것으로 사료된다.

• 한국식품영양학회지
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• 제7권4호
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• pp.345-352
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• 1994

High protein beverage of cow-soy milk was prepared by mixing the soymilk and commercial homogenized cow milk in the various ratios. Effect of heat treatment, pH and addition of calcium and sucrose was studied on the water-soluble nitrogen of cow-soy milk The heat-treated soymilk at 10$0^{\circ}C$ were centrifuged at the range of 830~29,900xg for 30 min and 11,200xg was found to be proper for determination of the degree of protein denaturation by centrifugal method. When soymilk was heated at 70~10$0^{\circ}C$ for 30~240 min, soluble nitrogen (QA SN) in supernatant of protein was decreased to 78.0~56.8% due to protein denaturation. Most of heat denaturation of protein was found to be occurred during Initial heating 10$0^{\circ}C$ for all mixed cow-soy milk. The sedimentation of SN was maximum at pH 4.0 In the range of pH 3~8. Addition of sucrose affected little on oASN while calcium addition reduced %SN significantly to approx. 55% for soymilk(100%). The effect of Ca was less as the ratio of cow milk increased.

• BMB Reports
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• 제36권4호
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• pp.367-372
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• 2003

The stability of four hemoglobins (Hb) in dimer forms (low concentration) were investigated by the kinetics of denaturation. The rate constants of denaturation were obtained by variation of 280 nm absorption versus time in 10 mM Tris-HCl, 10 mM EDTA, pH 8.0 at $45^{\circ}C$ in the absence and presence of 0.5 M ethanol, dimethyl sulfoxide (DMSO), formamide, and glycerol. The results show the trend of rate constants in different co-solvents in the following order: chicken hemolysate < human hemolysate and chicken Hb D < chicken Hb A. The buried surface area was calculated for Hb samples in the absence of cosolvents. Accordingly, the trend points out that: chicken Hb D > chicken Hb A > human Hb A. These results suggest that both chicken hemolysate and chicken Hb D are relatively more stable than human and chicken Hb A, respectively. However, the denaturation rate constants of Hb in different co-solvents have designated the following order: ethanol > DMSO > formamide > glycerol. As a matter of fact, this phenomenon is an indication of an increase in the denaturation capacity (DC) and hydrophobicity, and a decrease in the surface tension of the solution in the preceding co-solvents.

• 한국축산식품학회지
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• 제18권3호
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• pp.209-215
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• 1998

Effects of protein concentration, ionic strength, pH, and temperature range on the heat-induced denaturation of salt soluble protein extracted from spent layer meat were investigated. Viscosity of salt soluble protein heated at 65$^{\circ}C$ for 30 min began to increase sharply above 7 mg/ml of breast protein concentration, and above 21 mg/ml of leg protein concentration, respectively. Both turbidity and viscosity showed the highest value in cooked protein solution with pH 6.0 and 1% NaCl. The turbidity of salt soluble protein started to increase continuously from 40$^{\circ}C$ to 80$^{\circ}C$. The viscosity increased rapidly from 45$^{\circ}C$ to 60$^{\circ}C$ in breast protein, and increased from 50$^{\circ}C$ to 55$^{\circ}C$ in leg protein, respectively, and then kept relatively constant. Breast protein had higher viscosity than leg protein during heat-induced gelation. Therefore, salt soluble protein from spent layer meat was associated with denatured protein (turbidity change) prior to gelation (viscosity change) during heating. Breast protein showed lower thermal transition temperature, and better gel formation than leg protein during heating.

• 한국수산과학회지
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• 제42권6호
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• pp.574-579
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• 2009

Acid- and pepsin-solubilized collagens were extracted from the skin of shark (Isurus oxyrinchus) and their physicochemical properties were characterized by amino acid analysis, SDS-PAGE, the composition of collagen types, solubility and denaturation temperature. Acid - and pepsin-solubilized collagens from shark skin had an imino acid of 188.8 and 186.2 residues/1,000 amino acids, respectively. SDS-PAGE showed two different${\alpha}$ chains ($\alpha1$ and $\alpha2$) and $\beta$-component. The component ratio of type I and V was 10:1, and the type III was not found. Solubility of acid-soluble collagen was low in the range of pH 6.0 to pH 11.0. On the other hand, pepsin-solubilized collagen showed a low solubility in the range of pH 7.0-9.0. Temperature for denaturation of acid- and pepsin-solubilized collagens were $25^{\circ}C$ and $27^{\circ}C$, respectively.

• 한국응용곤충학회지
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• 제30권2호
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• pp.138-143
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• 1991

배추흰나비 P. rapae와 P. brassicae GV의 DNA성상과 이를 기초로한 상동성을 검정한 결과 Tm값에서는 P. rapae GV DNA는 $83.7^{\circ}C$이고, P. brassicae GV DNA의 경우는 $84.0^{\circ}C$로 G+C 함량은 전자가 35.5%, 후자가 35.9%였다. 그리고 제한산소처리에 의한 DNA의 분석에서는 P. Rapae GV의 genome의 크기는 103 kb, P. brassicae GV DNA는 108kb로 나타났으며, 두바이러스 간의 상동성은 97.0%였다.

• Journal of Applied Biological Chemistry
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• 제58권2호
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• pp.97-100
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• 2015

The thermostable pectinase gene TmPec isolated from Thermotoga maritima was introduced into the NdeI site of pRSET-B vector and expressed in its intact form in Escherichia coli BL21. The overexpressed intact form of pectinase (TmPecN protein) was partially purified by heat-denaturation procedure. TmPecN showed the highest activity between 85 and $95^{\circ}C$, and at approximately pH 6.5. Enzyme activity was stably maintained at temperatures below $85^{\circ}C$. In the presence of $Ca^{2+}$, pectinase activity of TmPecN increased to 128.4% of normal level. In contrast, $Ba^{2+}$, $Zn^{2+}$, and $Mn^{2+}$ strongly inhibited TmPecN activity. We conclude that the biochemical properties of the intact form of TmPecN are comparable to those of the recombinant protein TmPec reported previously.