pH值对纯化猪肉肌球蛋白热聚集体的影响

为研究pH值对肌球蛋白热聚集行为的影响,以纯化的猪肉肌球蛋白为对象,在体系pH值5.5,6,6.5,7,7.5,8,8.5条件下,采用动态光散射、差示荧光扫描仪、负染透射电镜等技术进行研究.结果 表明:pH值由5.5升至8.5,蛋白变性温度由40.2℃降至36.9℃,Ca2+-ATP酶失活温度由40℃升至60℃,电镜观...     

不同离子强度下罗非鱼肌球蛋白热变性聚集研究

以罗非鱼肉为原料,提取肌球蛋白,分析不同离子强度(1、50、150、300、600 mmol/L KCl)下热处理(40~80℃,1℃/min)对其浊度、溶解度、表面疏水性、α-螺旋含量及聚集体粒径的影响。结果显示,离子强度及热处理温度明显影响肌球蛋白的热变性聚集。在低离子强度(1~150 mmol/L KCl)下,肌球蛋白聚集成纤丝,溶解性差,热处理后分子聚集沉淀,溶解度和α-螺旋含量减小(p0.05),体系热稳定性差;在高离子强度(300~600 mmol/L KCl)下,肌球蛋白分子解离成单体,溶液澄清,当热处理温度高于50℃时,肌球蛋白溶解度下降,表面疏水性增加,α-螺旋含量显著减小(p0.05),但分子聚集不明显。总体分析,高盐离子的静电屏蔽作用导致肌球蛋白纤丝解离,由此也会对肌球蛋白分子结构有一定的保护作用,热稳定性相对较好。     

L-赖氨酸对鲢肌球蛋白热聚集行为的影响

研究外加L-赖氨酸（L-Lys）对鲢肌球蛋白热聚集行为的影响。将浓度为1、5、10、20?mmol/L的L-Lys添加到肌球蛋白中,分别进行未加热（25?℃稳定30?min）、预加热（40?℃加热60?min）和二段式加热（40?℃加热60?min的基础上90?℃加热30?min）,测定其pH值、浊度、流变特性及凝胶强度的变化。结果表明：肌球蛋白溶液的pH值随L-Lys浓度的增加而增加;20?mmol/L的L-Lys能够显著降低肌球蛋白溶液在未加热状态下的浊度,1～20?mmol/L的L-Lys能够显著降低肌球蛋白溶液在加热过程中的浊度,尤其是二段式加热后的浊度;添加L-Lys后的肌球蛋白更偏向于黏性流体,成胶能力更弱,形成的凝胶强度更小。L-Lys作为一种常见的可溶性小分子添加剂,且为人体必须氨基酸之一,能够通过静电相互作用及改变肌球蛋白溶液的pH值抑制鲢肌球蛋白的热聚集行为,对其开发利用还有待进一步研究。     

硫酸葡聚糖对低离子强度下罗非鱼肌球蛋白热变性聚集的抑制及其机制

以罗非鱼背部白肉为原料提取肌球蛋白,分析在低离子强度(1,50,150 mmol/L KCl)下,硫酸葡聚糖(dextran sulfate,DS)的添加对热处理(40～80℃,1℃/min)过程中肌球蛋白(2.0mg/mL)溶解度和分子结构的影响,探讨DS对肌球蛋白热变性聚集的抑制效果及机理。结果表明,在1mmol/L KCl条件下,肌球蛋白溶解度极低,热处理后分子头部聚集,尾部交联;在50,150mmol/L KCl条件下,肌球蛋白纤丝逐渐解离变粗,热处理后丝状体消失,头部聚集,溶解度、α-螺旋含量明显下降。添加0.4mg/mL DS后,热处理过程中体系浊度、溶解度和α-螺旋含量无明显变化,与未添加DS的体系相比,相同温度条件下肌球蛋白的溶解度明显增大(P0.05),表面电势升高。DS与肌球蛋白分子间强的静电相互作用能有效抑制低离子强度下肌球蛋白的热变性聚集。     

原子力显微镜研究L-半胱氨酸对鲢肌球蛋白溶液热聚集行为的影响

利用原子力显微镜技术分析L-半胱氨酸（L-cysteine,L-Cys）对鲢肌球蛋白热聚集行为的影响。在肌球蛋白溶液中添加5?mmol/L（pH?7.0）的L-Cys溶液,分别进行未加热（25?℃、30?min）、一段式加热（90?℃、30?min）、二段式加热（40?℃、60?min＋90?℃、30?min）处理,分别测定溶解度、表面疏水性、聚集行为表面形貌的变化。结果表明：3?种加热方式低盐条件下L-Cys均显著提高肌球蛋白的溶解度（P＜0.05）;一段式加热时L-Cys显著提高高/低盐条件下肌球蛋白的表面疏水性（P＜0.05）,二段式加热时高盐条件下表面疏水性显著提高（P＜0.05）,其他条件下表面疏水性无明显变化。高/低盐条件下添加L-Cys均能显著改变肌球蛋白聚集行为的表面形貌,使聚集体更加分散,抑制了肌球蛋白的聚集。L-Cys对肌球蛋白溶解度、表面疏水性的影响进一步影响了其聚集行为,改变其聚集形貌。     

pH值对柞蚕蛹粉凝胶特性及蛋白质热聚集行为的影响

柞蚕蛹富含优质蛋白质,是一种具有很高开发利用价值的食品原料。采用质构仪、流变仪和激光扫描共聚焦显微镜等分析不同pH值对柞蚕蛹粉凝胶特性及蛋白质分子热聚集行为的影响。结果表明:pH值为7时形成的柞蚕蛹粉凝胶网络较为连续和均匀,凝胶保水性最高(51.67%±0.79%,P<0.05);pH值为9时的柞蚕蛹粉有最低的临界凝胶质量分数(8%)、最高的凝胶硬度(41.67N±3.37N,P<0.05)和弹性(2.81mm±0.07mm,P<0.05)。柞蚕蛹粉凝胶的储能模量与蛋白质的溶解度呈显著正相关(R=0.92,P<0.05),而与蛋白质的凝固率(R=-0.52)和表面疏水性(R=-0.77)呈显著负相关(P<0.05)。pH 值为9时,蛋白质溶解度最高(62.13%±0.63%,P<0.05),表面疏水性最低(70.06μg±9.32μg, P<0.05),形成了更多的小尺寸热聚集物并增强了凝胶基质;而在pH值为5时,蛋白质溶解度最低(28.96%±1.13%,P<0.05),表面疏水性最高(195.66μg±1.30μg,P<0.05),促使更多的大尺寸热聚集物形成并无序堆叠而削弱凝胶基质。研究旨在通过调节pH值控制柞蚕蛹粉中蛋白质的热聚集行为,进而获得理想质地和保水性的柞蚕蛹粉凝胶。     

大豆蛋白的热处理改性及热聚集行为研究进展

大豆蛋白的热处理改性有助于提高其功能特性及生物有效利用率,从而拓宽其在食品工业中作为配料应用的范围。热处理主要通过对大豆蛋白热聚集行为的影响,从而达到影响大豆蛋白功能性质及生物有效利用率的目的。因此,本文拟对大豆蛋白的热处理改性及大豆蛋白(包括大豆分离蛋白、大豆球蛋白及大豆伴球蛋白)的热聚集行为的研究进展进行综述。希望通过对上述方面的综述,能为广大科研人员及企业生产单位提供一定的借鉴。     

蛋清蛋白质热处理改性及其热聚集行为的 研究进展

蛋清蛋白质的热处理改性有助于提高其功能特性及生物有效利用率, 从而拓宽其在食品工业中作为配料的应用范围。热处理主要通过对蛋清蛋白质热聚集行为的影响, 从而影响其在食品体系中的应用, 而对蛋白质聚集行为的研究将有助于改善食品体系中蛋白质的功能性质。蛋清粉是许多食品加工中的重要原料, 也是很好的蛋白质体系, 是食品蛋白质热聚集行为和功能性构效关系的理想研究对象。对蛋清蛋白质聚集机制的研究将有助于功能性蛋制品的开发。因此, 本文主要对蛋清蛋白质热聚集行为的研究进行综述, 希望能为相关科研人员及企业提供一定的借鉴。     

低场核磁共振研究pH值对兔肌球蛋白热凝胶特性的影响

研究pH值对兔骨骼肌肌球蛋白热诱导凝胶保水性以及水分移动性的影响。运用低场核磁共振测定肌球蛋白凝胶中水的T2弛豫时间,同时测量保水性和硬度并观察凝胶超微结构。核磁共振结果拟合后发现,对应不可移动水和自由水的T22和T23弛豫时间随着pH值升高而降低,说明水分的移动性随着肌球蛋白所带负电荷数目增加而减弱;主成分分析结果发现,T22和T23弛豫时间与保水性、硬度和凝胶孔径有较强的相关性;位于等电点附近的样品在样品评分图上与其他样品有显著不同。肌球蛋白的蛋白质分子表面电荷数量和分布影响了蛋白质分子卷曲和伸展的情况,对最终凝胶保水性、硬度和网孔直径有很大影响,而T2弛豫时间则能很好的反映这种变化趋势。     

蛋清蛋白质热处理改性及其热聚集行为的研究进展

蛋清蛋白质的热处理改性有助于提高其功能特性及生物有效利用率,从而拓宽其在食品工业中作为配料的应用范围。热处理主要通过对蛋清蛋白质热聚集行为的影响,从而影响其在食品体系中的应用,而对蛋白质聚集行为的研究将有助于改善食品体系中蛋白质的功能性质。蛋清粉是许多食品加工中的重要原料,也是很好的蛋白质体系,是食品蛋白质热聚集行为和功能性构效关系的理想研究对象。对蛋清蛋白质聚集机制的研究将有助于功能性蛋制品的开发。因此,本文主要对蛋清蛋白质热聚集行为的研究进行综述,希望能为相关科研人员及企业提供一定的借鉴。     

Thermal Aggregation of Myosin Subfragments from Cod and Herring

Turbidity of fish myosin subfragment solutions increased with temperature, except cod heavy meromyosin turbidity leveled above 45°C. Extent of aggregation and number of cross-linking sites for cod heavy and light meromyosins were significantly higher than for herring (p<0.05), but only at temperatures above 35°C and 45°C, respectively. Thermal aggregation ability increased linearly with increased surface hydrophobicity (S_o) for the myosin subfragments, except cod heavy meromyosin where the increase in S_o between 45–55°C did not correspond to an increase in cross-linking ability. The lessened aggregation ability of herring myosins may be due to the low cross-linking of the HMM (S-2) region.     

Role of Cooling Process in the Thermal Aggregate Formation by Carp Myosin Rod

Carp myosin rod solution did not show detectable turbidity upon heating at 80 °C. Rod aggregation was detected only by high sensitive light scattering intensity and gel filtration analysis on Sepharose CL 4B. Roughly half of myosin rod was still monomeric for sample heated at 80 °C at 2 mg/mL. Prolonged heating at 80 °C did not increase the amount of aggregates. Aggregation was prominent at high concentration of rod. Rod aggregation was promoted by cooling of the heated rod solution. Heating at 80 °C completely unfolded the α‐helix structure of rod. However, α‐helix structure was significantly recovered by about 85% upon cooling. Unfolding and aggregation analysis revealed that complete unfolding of whole rod structure was needed for aggregation, and the cooling process accompanying refolding of helical structure was important for aggregate formation.     

Effect of Hydrostatic Pressure on Aggregation and Viscoelastic Properties of Tilapia (Orechromis niloticus) Myosin

ABSTRACT: Hydrostatic pressures from 500 to 2000 atmospheres (atm) were applied at 0°C to determine the aggregation and viscoelastic properties of tilapia ( Orechromis niloticus ) myosin. Native myosins were present as long, linear, and single filaments. After a 500-atm treatment, these filaments unfolded and their volume decreased. Upon 1000-atm and 1500-atm treatments, myosins aggregated and formed inseparable network structures. Further, they transformed from viscous sol to elastic gels with a pressure of 500 to 1000 atm. At 2000 atm, the myosin formed irregular aggregates. This study reveals that at 500 atm, myosins unfolded; at 1000 atm, they aggregated, and beyond 1500 atm, they formed both a precipitate and gel.     

Thermal Aggregation Properties of Duck Salt-Soluble Proteins at Selected pH Values

Thermal aggregation properties of duck breast and leg salt-soluble proteins (SSP) were studied at pH 5.50, 5.75 and 6.00. At pH 5.50, a major transition for breast was observed at 60.3°C and for leg at 41.8°C. At pH 5.75, major transitions at 44.6 and 43.2°C were obtained, respectively, for the breast and leg SSP. Three transitions at 46.0, 53.0 and 59.0°C were exhibited by breast SSP at pH 6.00, whereas only two major transitions at 47.4 and 54.0°C were identified in leg SSP. Changes in transition peak heights and shifts in transition temperatures as a result of pH changes indicated that, depending on fiber type, pH may enhance or suppress the aggregation behavior of specific constituents of the myosin/actomyosin complex, thereby altering the overall aggregation pattern of the protein preparation.     

Quantitative Estimation of Dark Muscle Content in the Mackerel Meat Paste and its Products Using Antisera Against Myosin Light Chains

ABSTRACT: Based on the high level of extractability of myosin subunits (light chains), even after prolonged heat treatment of muscle, a new method to evaluate the dark muscle content in the fish meat and products of mackerel is proposed. Tissue-specific rabbit antisera with myosin light chains (A1 from ordinary muscle and D1 from dark muscle) from mackerel Scomber japonicus were obtained. Mackerel meat paste (surimi) was dissolved in 8 M urea containing 1% SDS, and diffused on agar plates containing antiserum against A1 or D1 by single radial immunodiffusion (SRID). The results obtained showed that the area of halos formed in the plates was quite proportional to the content of dark muscle.     

Fish Myosin Aggregation as Affected by Freezing and Initial Physical State

ABSTRACT: Fish myosin obtained from Tilapia nilotica was solubilized in 20 mM Tris-HCl, pH 7.0, with 0.6 M KCl (solution model system), or suspended without salt (suspension model system). Changes in % soluble protein, Ca²⁺-ATPase activity, and total and reactive -SH groups during frozen storage were evaluated. Frozen induced aggregation of fish myosin showed different behavior depending upon its initial physicochemical state. When myosin was solubilized prior to frozen storage, head-to-head interactions seemed to be more involved in protein aggregation with a strong participation of disulfide bonds. On the contrary, a preferentially side-to-side mechanism might be involved in the aggregation of myosin upon suspension, with a minor interaction of -SH groups.