超声波对肌原纤维蛋白热诱导凝胶化学作用力与保水性的影响

【目的】研究超声波对肌原纤维蛋白凝胶化学作用力与保水性的影响,并探讨化学作用力与保水性之间的内在联系。【方法】取活AA鸡屠宰,提取肌原纤维蛋白(myofibrillar proteins,MP),用不同超声时间处理MP并制成热诱导凝胶,运用凝胶中总巯基含量的变化来反应二硫键的形成;凝胶的表面疏水性S0和Zeta电位值来表征疏水作用力和静电斥力;用拉曼光谱的I850/I830比值大小反映凝胶氢键的变化;凝胶保水性用高速离心机测定。【结果】超声波处理0—6 min时,MP凝胶的总巯基含量随时间的增加而减少,活性巯基含量显著增加;处理6—15 min时,MP凝胶的总巯基以及活性巯基均随时间延长而显著减少,而对MP原料进行同样处理时,处理时间在0—6 min内,MP总巯基和活性巯基变化趋势与MP凝胶相同;超过9 min后,活性巯基和总巯基没有显著变化,且二者含量逐渐接近。表明短时间超声波处理促进了MP分子内部巯基转变成二硫键,长时间超声波处理和加热成胶的共同作用促进了活性巯基转变成二硫键。MP凝胶的表面疏水性先随超声时间延长从1 194.1显著上升到1 489.5(6 min),随后逐渐降至1 230.8,表明超声波产生的空穴效应能够使MP分子内部疏水基团暴露到分子表面,但超过6 min后,增加的蛋白表面疏水性又被包裹在凝胶网络中。MP凝胶的Zeta电位绝对值随超声时间的增加从6.03显著增加到7.68(P0.05),超过6 min后显著减少,表明超声波处理使MP分子逐渐展开,蛋白质分子间静电作用增强,但过度展开后对其形成凝胶的静电作用力不利。适度的超声时间(0—6 min)使MP凝胶的归一化强度I850/I830比值从0.9805增加至1.023(P0.05),表明MP与水分子形成的"蛋白-水分子"氢键增多,6 min过后比值减少,蛋白与水分子之间的氢键减弱;超声波处理0—6 min后的MP凝胶保水性从47.5899%快速升至72.9855%(6 min)(P0.05),之后随时间延长,凝胶的保水性减少至44.356%。相关性分析结果表明,保水性与总巯基的相关性不大(P0.05),与活性巯基显著相关(P0.05),与表面疏水性、电位绝对值和氢键都极显著相关(P0.01)。【结论】超声波显著影响肌原纤维蛋白凝胶化学作用力与保水性;疏水作用力、静电斥力和氢键是决定保水性的主要作用力,而二硫键次之;超声波处理时间为6 min时为最优条件,在此条件下,凝胶的疏水作用力、氢键和静电斥力均达到最大,致使凝胶网络结构均匀致密,能最大限度的保留水分。     

Subkelvin cooling NO molecules via "billiard-like" collisions with argon

We report the cooling of nitric oxide using a single collision between an argon atom and a molecule of NO. We have produced significant numbers (108 to 109 molecules per cubic centimeter per quantum state) of translationally cold NO molecules in a specific quantum state with an upper-limit root mean square laboratory velocity of 15 plus or minus 1 meters per second, corresponding to a 406 plus or minus 23 millikelvin upper limit of temperature, in a crossed molecular beam apparatus. The technique, which relies on a kinematic collapse of the velocity distributions of the molecular beams for the scattering events that produce cold molecules, is general and independent of the energy of the colliding partner.     

分子动力学模拟解析脉冲电场对类PSE鸡肉肌球蛋白凝胶特性作用规律

【目的】以类PSE鸡肉肌原纤维蛋白为研究对象,通过分子动力学模拟技术研究脉冲电场处理对其凝胶特性和构象修饰的影响,并对凝胶特性改变的潜在机制进行阐述,以此拓宽这种新兴食品加工技术的工业应用,为禽类加工方向提高异常肉制品的经济效益提供一种新的方法。【方法】本试验选取类PSE鸡肉为原料并提取其肌原纤维蛋白,对比8、18和28 kV·cm^-1电场强度下脉冲电场(脉冲电场频率为800 Hz,占空比47%)处理及非脉冲电场处理的类PSE鸡肉肌原纤维蛋白不稳定动力学指数、流变学特性及通过分子动力学技术建立电场强度18 kV·cm^-1的脉冲电场模拟体系,通过收集模拟过程中的均方根偏差(RMSD)、均方根波动(RMSF)和对蛋白质总体构象的观察的变化来阐明在该条件下脉冲电场处理对类PSE鸡肉肌原纤维蛋白分子构象动态变化的作用机制。研究脉冲电场作用对类PSE鸡肉肌原纤维蛋白构象稳定性、保水性、流变特性的影响。【结果】不同电场强度的脉冲电场处理后的类PSE鸡肉肌原纤维蛋白体系不稳定动力学曲线斜率更小,蛋白体系相较于未经处理的样品更加稳定。蛋白凝胶的保水性结果为1...     

Spectroscopic detection of stratospheric hydrogen cyanide

A number of features have been identified as absorption lines of hydrogen cyanide in infrared spectra of stratospheric absorption obtained from a high-altitude aircraft. Column amounts of stratospheric hydrogen cyanide have been derived from spectra recorded on eight flights. The average vertical column amount above 12 kilometers is 7.1 +/- 0.8 x 10(14) molecules per square centimeter, corresponding to an average mixing ratio of 170 parts per trillion by volume.     

Renewable hydrogen from nonvolatile fuels by reactive flash volatilization

Droplets of nonvolatile fuels such as soy oil and glucose-water solutions can be flash evaporated by catalytic partial oxidation to produce hydrogen in high yields with a total time in the reactor of less than 50 milliseconds. Pyrolysis, coupled with catalytic oxidation of the fuels and their fragments upon impact with a hot rhodium-cerium catalyst surface, avoids the formation of deactivating carbon layers on the catalyst. The catalytic reactions of these products generate approximately 1 megawatt of heat per square meter, which maintains the catalyst surface above 800 degrees C at high drop impact rates. At these temperatures, heavy fuels can be catalytically transformed directly into hydrogen, carbon monoxide, and other small molecules in very short contact times without the formation of carbon.     

温室湿度环境的主成分分析人工神经网络建模研究

实测温室内影响空气湿度的环境因子组成数据样本,对数据样本进行主成分分析,提取出影响温室湿度的4个主要成分．讨论提取的主成分与原始过程数据样本间的关系。以采用主成分分析后的数据样本作为神经网络模型的输入变量,模型模拟值和实测值之间的相关系数R^2为0．8842。以±0．1作为模拟相对误差,命中率达到85％。用训练后的网络模型对20组未参加建模的样本数据进行模拟,均方根误差为1．6745,优于回归方程法的4．4349。基于神经网络模型,运用敏感性分析法对影响湿度的各医素进行重要性分析和排序,得出各影响因素的重要程度依次为室内温度、室外湿度、室外温度、保温帘展开度、室外风速、室外太阳辐射照度、天窗开窗角度和侧窗开窗角度．     

Jovian Atmosphere: Structure and Composition between the Turbopause and the Mesopause

The occultation of the star Beta Scorpii by Jupiter was observed at high time resolution in three wavelength channels. The results imply a temperature of 220 degrees K at an altitude in the Jovian atmosphere corresponding to 10(14) molecules per cubic centimeter, and temperature fluctuations of 2 degrees to 10 degrees K over vertical scales of 2 to 10 kilometers. They suggest that the vertical eddy diffusion coefficient near the turbopause has a lower limit of 7 x 10(5)K square centimeters per second, and that the turbopause lies above the altitude where the density is 5 x 10(13) molecules per cubic centimeter. Below the turbopause, the ratio of hydrogen to helium is consistent with cosmic abundances.     

Modeling Study of Fruit Morphological Formation in Melon

Modeling of fruit morphological formation in melon is important for realizing virtual and digital plant growth. The objective of this study was to characterize the changes in patterns of fruit growth characters during plant development. In cultivar experiments, a high-resolution wireless vision sensor network has been developed to realize non-contact automatic uninterrupted measurement of the fruit shape micro-change (fruit size, color, and net). Results showed that the fruit swelling process (vertical and horizontal diameters) exhibited a slow-rapid-slow pattern, which could be well described with a logistic curve against growing degree days (GDD); fruit color changes based on the RGB values could be represented by quadratic relationship to cumulative GDD; the fruit net changes over growth progress could be partitioned into three phases according to the time interval. The first phase was from 1 to 30 days after pollination (DAP), in which the vertical stripe appeared at fruit middle part and the horizontal stripe at fruit petiole and hilum part as well; the second phase was from 30 to 40 DAP, the horizontal stripe occurred at fruit middle part and the net was formed; the third phase was the process started from 40 DAP, the netted breadth and thickness were gradually increased. The model was validated with the independent data from the experiment, and the mean RMSE (root mean square error) of fruit were 0.36 and 0.28 cm for vertical and horizontal diameters, 11.9 for fruit color, and 0.45 cm for stripe length and diameter at varied GDD, respectively.This work is beneficial to a reliable foundation for study the relationship between morphological formation and physiological change of the melon fruit internally and then realize the intelligent precision management to improve the yield and quality of greenhouse melon production.     

Polymerization-induced epitaxy: scanning tunneling microscopy of a hydrogen-bonded sheet of polyamide on graphite

A molecularly thin film of a two-dimensional polymer network formed by hydrogen bonding was synthesized and investigated with scanning tunneling microscopy. Poly(in-caprolactam) (nylon 6) was epitaxially grown on the basal plane of graphite and an ultrathin film of the polymer was obtained after the bulk materials had been washed away with solvents. The polymer chain has a planar, all-trans conformation and adjacent chains run in the antiparallel direction. This produces complete pairing of hydrogen bonding groups, with each amide group lying on a straight line perpendicular to the polymer backbone. This hydrogen-bonded sheet is oriented so that each polymer backbone lies in the (1010) direction on the graphite hexagonal lattice, as opposed to the (1120) direction taken by other paraffinic molecules studied so far. This experiment shows that hydrogen bonding can be used to control the orientation of macromolecules in two dimensions.     

C 2H 5N 4- C 6H 3N 3O-7氢键相互作用的理论研究

运用密度泛函理论方法,在B3LYP/6-311++G**水平上对4-氨基-1,2,4-三唑阳离子(AT)和2,4,6-三硝基苯酚阴离子(PA)形成的氢键二聚体进行理论计算研究.计算得到4种稳定结构的氢键复合物及最稳定异构体D1的振动频率、电子吸收光谱与热力学性质.结果表明,氢键复合物中存在较强的N—H…O与C—H…O红移氢键.经过基组重叠误差和零点振动能校正后,D1的氢键相互作用能为-30.71kJ/mol.热力学计算显示,在298.15K和标准状态下,D1气态氢键复合物分子的形成过程是放热、熵减小的非自发过程,但在低温下能自发进行.D1分子的标准摩尔生成焓和标准摩尔生成自由能分别为98.7,474.4kJ/mol.     

不同栽培模式对夏玉米根系性能及产量和氮素利用的影响

【目的】研究不同栽培模式对夏玉米根系性能、籽粒产量形成以及氮素吸收利用的影响,探明不同栽培模式下玉米根系形态特征与产量形成、氮素吸收能力的关系,为促进玉米根系生长发育、增强根系吸收性能、优化施肥量,促进玉米高产高效生产提供理论依据。【方法】在定位试验条件下,选用郑单958为试验材料,在两种地力条件下,以不施氮肥处理为对照(CK),设置超高产玉米栽培模式(SH)、高产高效栽培管理模式(HH)、农民习惯栽培管理(FP)3种栽培模式,比较分析不同栽培模式夏玉米根系特性对产量形成和氮素吸收利用的调控效应。【结果】不同栽培模式间夏玉米产量存在显著差异,与HH、FP和CK模式相比较,高地力和低地力田块SH模式的两年平均产量分别提高3.54%、17.50%、30.12%和3.16%、18.45%、27.72%,统计分析表明地力和栽培模式均对夏玉米产量有极显著影响,两种因素综合影响因年份变化有所差异。两种地力条件下,夏玉米各时期群体生物量均表现为SHHHFPCK。在抽雄期(VT)和完熟期(R6),SH处理的植株氮素积累总量显著高于其他处理,氮肥利用效率和氮肥农学利用效率均高于FP模式,HH模式的氮肥农学利用效率、氮肥利用效率和氮收获指数均最高,氮肥偏生产力低于FP模式,但仍高于SH模式。在不同地力基础上夏玉米不同栽培模式的根系指标变化趋势基本一致,在大喇叭口期(V12)、抽雄期(VT)、乳熟期(R3)的根系干重密度、根长密度和根表面积密度均为SHHHFPCK,从V12到VT期,SH和HH模式的根长密度、根干重密度和根表面积密度增幅均显著高于FP模式,从VT到R3期,降幅均显著低于FP模式,SH和HH模式VT期根系活跃吸收面积比例显著高于FP模式。不同栽培模式各时期根长密度、根表面积密度和根干重密度与产量和氮肥利用效率均呈显著正相关。【结论】高产高效栽培模式可以有效地促进根系发育、延缓根系衰老、提高氮肥利用效率,有助于实现夏玉米高产高效的目标。     

Palladium-catalyzed aerobic dehydrogenation of substituted cyclohexanones to phenols

Aromatic molecules are key constituents of many pharmaceuticals, electronic materials, and commodity plastics. The utility of these molecules directly reflects the identity and pattern of substituents on the aromatic ring. Here, we report a palladium(II) catalyst system, incorporating an unconventional ortho-dimethylaminopyridine ligand, for the conversion of substituted cyclohexanones to the corresponding phenols. The reaction proceeds via successive dehydrogenation of two saturated carbon-carbon bonds of the six-membered ring and uses molecular oxygen as the hydrogen acceptor. This reactivity demonstrates a versatile and efficient strategy for the synthesis of substituted aromatic molecules with fundamentally different selectivity constraints from the numerous known synthetic methods that rely on substitution of a preexisting aromatic ring.     

Escape of hydrogen from venus

Recombination of O(2)(+) represents a source of fast oxygen atoms in Venus' exosphere, and subsequent collisions of oxygen atoms with hydrogen atoms lead to escape of about 10(7) hydrogen atoms per square centimeter per second. Escape of deuterium atoms is negligible, and the ratio of deuterium to hydrogen should increase with time. It is suggested that the mass-2 ion observed by Pioneer Venus is D(+), which implies a ratio of deuterium to hydrogen in the contemporary atmosphere of about 10(-2), an initial ratio of 5 x 10(-5) and an original H(2)O abundance not less than 800 grams per square centimeter.     

基于PCA-BPNN的温室番茄果实直径预测模型

[目的]研究温室番茄果实直径变化量的动态预测模型,为番茄所需水肥规律提供数据支持.[方法]选择番茄果实横径为研究对象,以5株番茄果实膨大期的数据建立模型,采用主成分分析法对植物生理生态信息和环境信息进行分析,提取主要成分,以主成分为自变量,输出变量为因变量,建立一个包含空气温度、空气湿度、土壤含水率、叶片温度及果实横径...     

Crystal structure of a complex of acridine, cytosine and water (1:1:1)

X-ray structural analysis of a crystalline complex between acridine C(13)H(9)N, cytosine C(4)H(5)N(3)O, and water (1:1:1) has been completed. The cytosine and water molecules form a sheet-like structure through a series of hydrogen bonds. The acridine molecules are bound to this layer through a hydrogen bridge from the water to the ring nitrogen. The acridine molecules stack in a parallel fashion normal to the cytosine-water sheets, with an average interplanar spacing of 3.5 angstroms.     

Dynamics of hydrogen bromide dissolution in the ground and excited states

The dissolution of acids is one of the most fundamental solvation processes, and an important issue is the nature of the hydration complex resulting in ion pair formation. We used femtosecond pump-probe spectroscopy to show that five water molecules are necessary for complete dissolution of a hydrogen bromide molecule to form the contact ion pair H+.Br-(H2O)n in the electronic ground state. In smaller mixed clusters (n < 5), the ion pair formation can be photoinduced by electronic excitation.     

Endogenous nitric oxide and hydrogen peroxide detection in indole-3-butyric acid-induced adventitious root formation in Camellia sinensis

Nitric oxide(NO)and hydrogen peroxide(H_2O_2)are essential signaling molecules with key roles in auxin induced adventitious root formation in many plants.However,whether they are the sole determinants for adventitious root formation is worth further study.In this study,endogenous NO and H_2O_2 were monitored in tea cutting with or without indole-3-butyric acid(IBA)treatment by using the fluorescent probes diaminofluorescein diacetate(DAF-2DA)and 2’,7’-dichlorodihydrofluorescein diacetate(DCF-DA),respectively.The overproduction of NO and H_2O_2 was detected in the rooting parts of tea cuttings treated with or without IBA.But little NO and H_2O_2 was detected before the initiation phase of tea cuttings even with IBA treatment indicating that they might be not directly induced by IBA.Further carbon and nitrogen analysis found that the overproduction of NO and H_2O_2 were coincident with the consumption of soluble sugars and the assimilation of nitrogen.These results suggest that rooting phases should be taken into consideration with the hypothesis that auxin induces adventitious root formation via NO-and H_2O_2-dependent pathways and sink establishment might be a prerequisite for NO and H_2O_2 mediated adventitious root formation.     

基于微波辐射计SSM/I的海面风速反演算法研究及应用

海面风速是海洋环境的重要参数,微波辐射计是卫星监测海面风速的重要手段。通过微波辐射计SSM/I（Special Sensor Microwave/Imager）亮温与浮标实测风速建立的匹配数据集,利用人工神经网络构建海面风速反演模型。比较不同模型的反演效果,得出七通道单参数神经网络模型SANN（Singleparameter Artificial Neural Network ）反演的效果和浮标实测风速较为接近,均方根误差RMSE（Root Mean Square Error）为1.40m/s。因此选择该模型反演全球的月平均风速,并将反演结果与NOAA产品风速比较。结果表明：两者在整体分布和纬度平均上非常接近,均方根误差为1.03m/s。可见,该算法用于海面风速反演还是可行的。     

刺云实胶对魔芋葡甘聚糖分子链拓扑缠结的分析

将魔芋葡甘聚糖(KGM)与刺云实胶(TG)以一定的比例复配,通过旋转流变仪测定KGM-TG复配体系的相关流变特性,结合分子动力学和拓扑分析学研究KGM和TG分子的作用方式,探讨刺云实胶对魔芋葡甘聚糖分子链拓扑缠结的作用机理。结果表明,刺云实胶与KGM分子间存在协同增效作用,分子链间的主要作用是氢键作用力,刺云实胶的添加使得KGM分子链间的拓扑缠结强度与密度的增强,复配体系的力学性能得到加强。从分子作用本质上验证了刺云实胶与KGM之间流变性能的理化实验结果。