freezing

冻结
  • 文章类型: Journal Article
    步态冻结(FoG)对于患有帕金森氏病(PD)的人来说是一个重要问题,因为它是跌倒的主要原因,并且与不良的生活优势有关。底层设备仍未被理解;然而,据推测,它与认知障碍有关,即执行和视觉空间功能的损伤。在FoG发作期间,患者可能会有跌倒的风险,这显著影响了他们的生活质量。
    这项研究旨在系统地评估机器学习方法在FoG事件发生之前准确预测的有效性。该系统使用从Kaggle存储库收集的数据集进行了测试,包括从患有FoG发作的人的下背部收集的3D加速度计数据。在帕金森病患者中经常出现的严重适应症。通过测量65名患者和20名健康的老年人在从事模拟日常生活任务时的加速度来获取数据。在所有参与者中,45显示出FoG的适应症。这项研究利用了七种机器学习方法,即决策树,随机森林,近邻算法,LightGBM,和CatBoost模型。应用门控递归单元(GRU)-变压器和长期递归卷积网络(LRCN)模型来预测FoG。计划了构造和模型参数,以通过减轻计算难度和评估持续时间来提高性能。
    决策树表现出卓越的性能,在准确度方面实现91%的灵敏度,精度,召回,FoG的F1得分指标,过渡,和正常活动课程,分别。已经注意到,该系统具有客观和精确地预测FoG的能力。该系统将有助于促进对FoG的理解和处理的考虑。
    UNASSIGNED: Freezing of gait (FoG) is a significant issue for those with Parkinson\'s disease (PD) since it is a primary contributor to falls and is linked to a poor superiority of life. The underlying apparatus is still not understood; however, it is postulated that it is associated with cognitive disorders, namely impairments in executive and visuospatial functions. During episodes of FoG, patients may experience the risk of falling, which significantly effects their quality of life.
    UNASSIGNED: This research aims to systematically evaluate the effectiveness of machine learning approaches in accurately predicting a FoG event before it occurs. The system was tested using a dataset collected from the Kaggle repository and comprises 3D accelerometer data collected from the lower backs of people who suffer from episodes of FoG, a severe indication frequently realized in persons with Parkinson\'s disease. Data were acquired by measuring acceleration from 65 patients and 20 healthy senior adults while they engaged in simulated daily life tasks. Of the total participants, 45 exhibited indications of FoG. This research utilizes seven machine learning methods, namely the decision tree, random forest, Knearest neighbors algorithm, LightGBM, and CatBoost models. The Gated Recurrent Unit (GRU)-Transformers and Longterm Recurrent Convolutional Networks (LRCN) models were applied to predict FoG. The construction and model parameters were planned to enhance performance by mitigating computational difficulty and evaluation duration.
    UNASSIGNED: The decision tree exhibited exceptional performance, achieving sensitivity rates of 91% in terms of accuracy, precision, recall, and F1- score metrics for the FoG, transition, and normal activity classes, respectively. It has been noted that the system has the capacity to anticipate FoG objectively and precisely. This system will be instrumental in advancing consideration in furthering the comprehension and handling of FoG.
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  • 文章类型: Journal Article
    生活在季节性寒冷地区的低温动物必须适应季节变化和特定的环境条件。在冬天,一些两栖动物在陆地上冬眠,遇到有限的环境水,缺氧,极低的温度会导致全身冻结。这些压力会触发两栖动物的生理和生化适应,从而使它们得以生存。RanaSylvatica,俗称木蛙,表现出优异的耐冻性。他们可以将他们的代谢活动减慢到几乎停止,并在冬眠期间将其体内65-70%的水冻结为细胞外冰,当温度再次升高时恢复正常。为了研究耐冻木蛙的分子适应性,对缺氧后的青蛙肝脏组织进行了全面的蛋白质组学分析,脱水,或使用无标记LC-MS/MS蛋白质组学方法进行冷冻暴露。定量蛋白质组学分析显示,87、118和86种蛋白质在脱水时显著上调,缺氧,和冰冻的群体,提示潜在的保护功能。三种上调酶的存在,谷胱甘肽S-转移酶(GST),醛缩酶(ALDOA),和山梨糖醇脱氢酶(SORD),也得到了验证。对于所有的酶,冷冻和缺氧组肝脏的比酶活性明显高于对照组。这项研究表明,商品及服务税,ALDOA,SORD可能通过调节细胞解毒和能量代谢参与耐冻机制。
    Ectothermic animals that live in seasonally cold regions must adapt to seasonal variation and specific environmental conditions. During the winter, some amphibians hibernate on land and encounter limited environmental water, deficient oxygen, and extremely low temperatures that can cause the whole body freezing. These stresses trigger physiological and biochemical adaptations in amphibians that allow them to survive. Rana sylvatica, commonly known as the wood frog, shows excellent freeze tolerance. They can slow their metabolic activity to a near halt and endure freezing of 65-70% of their total body water as extracellular ice during hibernation, returning to normal when the temperatures rise again. To investigate the molecular adaptations of freeze-tolerant wood frogs, a comprehensive proteomic analysis was performed on frog liver tissue after anoxia, dehydration, or freezing exposures using a label-free LC-MS/MS proteomic approach. Quantitative proteomic analysis revealed that 87, 118, and 86 proteins were significantly upregulated in dehydrated, anoxic, and frozen groups, suggesting potential protective functions. The presence of three upregulated enzymes, glutathione S-transferase (GST), aldolase (ALDOA), and sorbitol dehydrogenase (SORD), was also validated. For all enzymes, the specific enzymatic activity was significantly higher in the livers of frozen and anoxic groups than in the controls. This study reveals that GST, ALDOA, and SORD might participate in the freeze tolerance mechanism by contributing to regulating cellular detoxification and energy metabolism.
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  • 文章类型: Journal Article
    冰核蛋白(INpro)触发与大气相关的过冷水滴的冻结,生物,和技术应用。从细菌丁香假单胞菌中分离出的INpro的高冰核活性可能与蛋白质在细菌膜或液滴的空气-水界面(AWI)上的聚集有关。这里,我们拍摄了冻结的开始,提供这些拟议机制的直接证据。高速低温显微镜检查确定了两个蛋白质排斥玻璃载玻片之间的液滴中冻结的开始位置。来自灭菌的丁香假单胞菌(Snomax)的INpro在统计学上有利于液滴的AWI处的成核。通过过滤或添加表面活性剂去除细胞碎片增加了AWI处成核事件的频率。另一方面,培养的完整细菌细胞或无脂液滴成核冰,对AWI没有亲和力。总的来说,我们提供了视觉证据,表明丁香假单胞菌的INpro在疏水界面引发冻结,如AWI或细菌膜,对INpro的应用具有重要的机械意义。
    Ice-nucleating proteins (INpro) trigger the freezing of supercooled water droplets relevant to atmospheric, biological, and technological applications. The high ice nucleation activity of INpro isolated from the bacteria Pseudomonas syringae could be linked to the aggregation of proteins at the bacterial membrane or at the air-water interface (AWI) of droplets. Here, we imaged freezing onsets, providing direct evidence of these proposed mechanisms. High-speed cryo-microscopy identified the onset location of freezing in droplets between two protein-repellent glass slides. INpro from sterilized P. syringae (Snomax) statistically favored nucleation at the AWI of the droplets. Removing cellular fragments by filtration or adding surfactants increased the frequency of nucleation events at the AWI. On the other hand, cultivated intact bacteria cells or lipid-free droplets nucleated ice without an affinity to the AWI. Overall, we provide visual evidence that INpro from P. syringae trigger freezing at hydrophobic interfaces, such as the AWI or the bacterial membrane, with important mechanistic implications for applications of INpro.
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  • 文章类型: Journal Article
    许多研究证实了细胞外囊泡(EV)参与哺乳动物精子细胞生理过程的调节。事实证明,它们参与了获能过程,肢端反应,和抗氧化。尽管人们对电动汽车的生物医学潜力(包括寻找新的生殖生物标志物)越来越感兴趣,细胞外精囊在冷冻保存过程中维持精液质量的作用尚未确定。因此,这项实验的目的是评估在调节牛精子线粒体膜电位中使用的有效性,并解释细胞冷冻保存过程中EV作用的机制。从公牛精液血浆中分离外泌体,测量,并用于补充剂。从西门塔尔公牛收集精液样本,稀释,并预先评估。然后将它们分成不含EV的相等部分或补充0.75;1.5和2.25mg/ml的EV。测试样品冷冻/解冻,线粒体膜电位,DNA完整性,和生存能力进行了评估。已确定EV对冷冻保存的精子结构具有积极作用。电动汽车的最有利水平为1.5mg/ml,这可以成功地提高细胞在冷冻/解冻过程中的冷冻稳定性。在这项研究中,从精子血浆中分离出的外泌体,并在延长剂中补充浓缩剂量用于精子冷冻,通过支持线粒体膜的潜力和保护精子的细胞质膜,显着提高了细胞的冷冻稳定性。
    Numerous studies confirm the involvement of extracellular vesicles (EVs) in the regulation of physiological processes of mammalian sperm cells. It has been proven that they take part in the processes of capacitation, acrosonmal reaction, and anti-oxidation. Despite growing interest in the biomedical potential (including the search for new reproductive biomarkers) of EVs, the role of extracellular seminal vesicles in maintaining semen quality during cryopreservation has not yet been established. Therefore, the objective of this experiment was to evaluate the effectiveness of the use in the regulation of the mitochondrial membrane potential of bovine sperm and to explain the mechanisms of EV action during cell cryopreservation. Exosomes were isolated from bull semen plasma, measured, and used for extender supplementation. Semen samples were collected from Simmental bulls, diluted, and pre-evaluated. Then they were divided into equal fractions that did not contain EVs or were supplemented with 0.75; 1.5 and 2.25 mg/ml of EVs. The test samples were frozen/thawed and the mitochondrial membrane potential, DNA integrity, and viability were evaluated. EVs have been established to have a positive effect on cryopreserved sperm structures. The most favourable level of EVs was 1.5 mg / ml, which can be successfully to improve cell cryostability during freezing/thawing. In this study, exosomes isolated from the sperm plasma and supplemented with a concentrated dose in the extender for sperm freezing were shown to significantly improve cryostability of cells by supporting the potentials of the mitochondrial membrane and protecting the cytoplasmic membrane of spermatozoa.
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  • 文章类型: Journal Article
    皮肤的选择对于体外渗透测试(IVPT)至关重要。目的探讨不同冻融过程对皮肤屏障功能和格拉司琼、利多卡因透皮通透性的影响。大鼠和无毛小鼠皮肤在-20℃冷冻9天后在三种不同条件下解冻:4℃解冻,室温(RT),和32℃。新鲜样品和解冻样品之间的药物稳态通量没有显着差异,但与新鲜皮肤相比,格拉司琼在室温和32℃解冻的大鼠皮肤中的渗透滞后时间存在显着差异。组织学研究和扫描电镜图像显示冻融皮肤无明显结构损伤,而紧密连接(TJ)蛋白Cldn-1的免疫组织化学染色和酶联免疫吸附试验显示表皮屏障明显受损。结论是,冻融过程增加了亲水性药物的扩散速率,部分原因是TJ的功能降解。它建议无毛,应使用近交系和相同的动物供体,选择的皮肤解冻方法应在IVPT之前进行验证,特别是亲水性药物。
    The selection of skin is crucial for the in vitro permeation test (IVPT). The purpose of this study was to investigate the influence of different freezing-thawing processes on the barrier function of skin and the transdermal permeability of granisetron and lidocaine. Rat and hairless mouse skins were thawed at three different conditions after being frozen at -20℃ for 9 days: thawed at 4℃, room temperature (RT), and 32℃. There were no significant differences in the steady-state fluxes of drugs between fresh and thawed samples, but compared with fresh skin there were significant differences in lag time for the permeation of granisetron in rat skins thawed at RT and 32℃. Histological research and scanning electron microscopy images showed no obvious structural damage on frozen/thawed skin, while immunohistochemical staining and enzyme-linked immunosorbent assay for the tight junction (TJ) protein Cldn-1 showed significantly impaired epidermal barrier. It was concluded that the freezing-thawing process increases the diffusion rate of hydrophilic drugs partly due to the functional degradation of TJs. It\'s recommended that hairless, inbred strains and identical animal donors should be used, and the selected thawing method of skin should be validated prior to IVPT, especially for hydrophilic drugs.
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  • 文章类型: Journal Article
    目的:评估安乐死洞穴蟑螂(CCs;Blaberusgiganteus)和马达加斯加嘶嘶声蟑螂(MHCs;Grompphadorhinaportentosa)的方法。据推测,两种建议的方法对于两种物种的人道大规模安乐死都是有效的。
    方法:约800CC。
    方法:将CC分成25、50、75、100和150克的重复组,并放入3.8L塑料袋中。27个MHC被分为2至3组。该研究于2023年1月至3月进行。所有CC组都以4L/min的速率暴露于100%二氧化碳(CO2),直到袋子充满。在1-L容器中的棉球上使用CO2或2mL异氟烷或CO2和异氟烷的组合类似地麻醉马达加斯加的嘶嘶声蟑螂。一旦蟑螂不动,进行了二次安乐死步骤。每个重量类别的一袋CC暴露于肥皂水(5%Dawn洗碗液),然后将第二个放入-80°C的冰箱中。将MHCs的容器均匀地暴露于2种安乐死方法。个体保持其二次安乐死方法30分钟。
    结果:无论每个袋子中的CC重量如何,对不动时间(1.8±0.4分钟[平均值±SD])没有影响。对于肥皂水,两种物种的失败率均为0.2%CI(-0.1%至1.5%[1/413]),而对于冷冻方法,则为0.5%CI(0.005%至1.9%[2/414])。这些结果支持在CC和MHC中使用两步安乐死方法。
    结论:这些方法将作为在蟑螂中人道大规模安乐死的基于证据的替代方法。
    OBJECTIVE: To evaluate methods for euthanizing cave cockroaches (CCs; Blaberus giganteus) and Madagascar hissing cockroaches (MHCs; Gromphadorhina portentosa). It was hypothesized that both suggested methods would be effective for humane mass euthanasia of both species.
    METHODS: Approximately 800 CC.
    METHODS: The CCs were separated into replicate groups of 25, 50, 75, 100, and 150 grams and placed into 3.8-L plastic bags. Twenty-seven MHCs were divided into groups of 2 to 3. The study took place from January to March 2023. All CC groups were exposed to 100% carbon dioxide (CO2) at a rate of 4 L/min until the bag was full. Madagascar hissing cockroaches were similarly anesthetized using either CO2 or 2 mL of isoflurane on a cotton ball in a 1-L container or a combination of CO2 and isoflurane. Once cockroaches were immobile, secondary euthanasia steps were performed. One bag of CCs per weight category was exposed to soapy water (5% Dawn dishwashing liquid), and the second was placed into a -80 °C freezer. The containers of MHCs were evenly exposed to the 2 euthanasia methods. Individuals remained in their secondary euthanasia method for 30 minutes.
    RESULTS: Regardless of the weight of the CCs within each bag, there was no impact on time (1.8 ± 0.4 minutes [mean ± SD]) to immobility. The failure rates for both species were 0.2% CI (-0.1% to 1.5% [1/413]) for soapy water and 0.5% CI (0.005% to 1.9% [2/414]) for the freezer method. These results support the use of both 2-step euthanasia methods in CCs and MHCs.
    CONCLUSIONS: These methods will serve as an evidence-based alternative for humane mass euthanasia in cockroaches.
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  • 文章类型: Journal Article
    冷适应细菌在极端寒冷和不同温度下生存的能力是由于其独特的属性,如细胞膜稳定性,肽聚糖生物合成的上调,细胞外聚合物的产生增加,和膜颜料的膨胀。各种冷适应蛋白质,包括冰核蛋白(INPs),抗冻蛋白(AFP),冷休克蛋白(Csps),和冷适应蛋白(CAPs),帮助细菌在这些环境中生存。为了使细胞在极端寒冷的条件下保持温度波动的稳定性,分子水平的生存策略及其机制在冰冻圈条件下的适应中起着重要作用。此外,多功能冷休克蛋白中存在的冷休克结构域在其适应策略中起着至关重要的作用。脂肽的重大贡献,渗透压,膜色素在极端环境中的生存中起着不可或缺的作用。这篇综述总结了冷适应细菌的进化史及其在恶劣的寒冷环境中茁壮成长的分子和细胞适应策略。它还讨论了产生的类胡萝卜素的重要性,脂质成分,冷冻保护剂,蛋白质,和与这种适应有关的监护人。此外,简要讨论了细胞内适应的功能和机制。通过了解其分子和细胞适应寒冷气候条件的内在机制,人们可以利用和探索其在各种生物技术应用及其进化旅程中的潜力。这篇综述将帮助生命科学界的所有分支了解嗜冷菌的基本微生物学及其在生命科学研究中的潜在前景。
    The ability of cold-adapted bacteria to survive in extreme cold and diverse temperatures is due to their unique attributes like cell membrane stability, up-regulation of peptidoglycan biosynthesis, increased production of extracellular polymeric substances, and expansion of membrane pigment. Various cold-adapted proteins, including ice-nucleating proteins (INPs), antifreeze proteins (AFPs), cold shock proteins (Csps), and cold-acclimated proteins (CAPs), help the bacteria to survive in these environments. To sustain cells from extreme cold conditions and maintain stability in temperature fluctuations, survival strategies at the molecular level and their mechanism play significant roles in adaptations in cryospheric conditions. Furthermore, cold shock domains present in the multifunctional cold shock proteins play crucial roles in their adaptation strategies. The considerable contribution of lipopeptides, osmolytes, and membrane pigments plays an integral part in their survival in extreme environments. This review summarizes the evolutionary history of cold-adapted bacteria and their molecular and cellular adaptation strategies to thrive in harsh cold environments. It also discusses the importance of carotenoids produced, lipid composition, cryoprotectants, proteins, and chaperones related to this adaptation. Furthermore, the functions and mechanisms of adaptations within the cell are discussed briefly. One can utilize and explore their potential in various biotechnology applications and their evolutionary journey by knowing the inherent mechanism of their molecular and cellular adaptation to cold climatic conditions. This review will help all branches of the life science community understand the basic microbiology of psychrophiles and their hidden prospect in life science research.
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  • 文章类型: Journal Article
    芽休眠的基本问题仍然存在,包括什么温度满足休眠要求(即,寒意积累)。最近的研究表明,冻结温度会促进寒冷的积累,而抗寒性会影响萌芽时间-用于休眠评估的表型。在这里,我们评估了在三种处理下,葡萄树(Vitishybrids)在整个寒冷积累过程中的芽抗寒性(CH)和萌芽反应:恒定(5°C),波动(每天-3.5至6.5°C),和现场条件(麦迪逊,WI,美国)。经历较低温度的冷却处理促进了抗寒性的更大增益(CHfield>CHflowating>CHconstant)。所有处理都减少了观察到的萌芽时间,并增加了寒意积累。然而,当调整萌芽时间以消除冷适应效应时,感知的治疗效果会发生变化。在三种经典的寒战模型中(北卡罗来纳州,犹他州,和动态),没有人能够正确描述对寒意积累的萌芽反应的调整时间。因此,提出了一种新的模型,该模型扩大了积冷温度的范围,使其包括冻结温度,并在波动的温度条件下增强了积冷。最重要的是,我们的分析表明,对不均匀适应的调整改变了寒战治疗的感知有效性.因此,芽休眠的未来工作将受益于同时评估抗寒性。
    Fundamental questions in bud dormancy remain, including what temperatures fulfill dormancy requirements (i.e., chill accumulation). Recent studies demonstrate freezing temperatures promote chill accumulation and cold hardiness influences time to budbreak - the phenotype used for dormancy evaluations. Here we evaluated bud cold hardiness (CH) and budbreak responses of grapevines (Vitis hybrids) throughout chill accumulation under three treatments: constant (5 °C), fluctuating (-3.5 to 6.5 °C daily), and field conditions (Madison, WI, USA). Chill treatments experiencing lower temperatures promoted greater gains in cold hardiness (CHfield>CHfluctuating>CHconstant). All treatments decreased observed time to budbreak with increased chill accumulation. However, perceived treatment effectiveness changed when time to budbreak was adjusted to remove cold acclimation effects. Among three classic chill models (North Carolina, Utah, and Dynamic), none were able to correctly describe adjusted time to budbreak responses to chill accumulation. Thus, a new model is proposed that expands the range of chill accumulation temperatures to include freezing temperatures and enhances chill accumulation under fluctuating temperature conditions. Most importantly, our analysis demonstrates adjustments for uneven acclimation change the perceived effectiveness of chill treatments. Therefore, future work in bud dormancy would benefit from simultaneously evaluating cold hardiness.
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  • 文章类型: Journal Article
    湖羊是一种以其高繁殖率而闻名的品种。一年四季都在发情期,其繁殖种群正在逐步扩大。然而,目前冷冻保存精液的技术效果有限,这阻碍了该物种的持续发展。目的探讨不同穿透性冷冻保护剂(CPAs)和蛋黄(EY)浓度对湖羊精液冷冻保存效果的影响,以确定最有效的组合。
    在这项研究中,甘油(GLY)的影响,乙二醇(EG),二甲基乙酰胺(DMA),二甲基亚砜(DMSO),不同比例的GLY和EG,通过检测精子总运动性(TM),研究EY对解冻后精子质量的影响,渐进运动(PM),直线速度(VSL),曲线速度(VCL),平均路径速度(VAP),头部侧向位移(ALH)的振幅,摆动运动系数(WOB),平均运动度(MAD),功能完整性(质膜完整性,顶体完整性)和活性氧(ROS)水平。
    当GLY和EG加在一起时,与其他浓度组相比,6%GLY显著(p<0.05)增加TM,PM,质膜完整性,和解冻精子的顶体完整性。此外,显著降低精子ROS水平(p<0.05)。在这项研究中,TM,6%EG的PM和膜完整性显著高于对照(p<0.05),1%GLY+5%EG和6%GLY+6%EG组。与其他浓度组相比,20%EY显著(p<0.05)提高了TM,PM,和解冻精子的质膜完整性。然而,顶体的完整性随着EY浓度的增加而增加。
    总而言之,与其他组相比,用含有6%GLY和20%EY的稀释剂稀释的解冻后的Huram精液表现出更高的质量。
    UNASSIGNED: The Hu sheep is a renowned breed known for its high reproductive rate. It is in estrus all year round, and its breeding population is gradually expanding. However, the current techniques for cryopreserving semen have limited effectiveness, which hinders the continuous development of this species. The purpose of this study is to explore the effects of different penetrating cryoprotectants (CPAs) and egg yolk (EY) concentrations on the cryopreservation of Hu ram semen to determine the most effective combination.
    UNASSIGNED: In this study, the effects of glycerol (GLY), ethylene glycol (EG), dimethylacetamide (DMA), dimethyl sulfoxide (DMSO), different proportions of GLY and EG, EY on sperm quality after thawing were investigated by detecting sperm total motility (TM), progressive motility (PM), straight-line velocity (VSL), curvilinear velocity (VCL), average path velocity (VAP), amplitude of lateral head displacement (ALH), wobble movement coefficient (WOB), average motion degree (MAD), functional integrity (plasma membrane integrity, acrosome integrity) and reactive oxygen species (ROS) level.
    UNASSIGNED: When GLY and EG were added together, compared to other concentration groups, 6% GLY significantly (p < 0.05) increased TM, PM, plasma membrane integrity, and acrosome integrity of thawed sperm. Additionally, it significantly (p < 0.05) decreased the ROS level of sperm. In this study, the TM, PM and membrane integrity of the 6% EG were significantly (p < 0.05) higher than those of the control, 1% GLY+5% EG and 6% GLY+6% EG groups. Compared to other concentration groups, 20% EY significantly (p < 0.05) improved the TM, PM, and plasma membrane integrity of thawed sperm. However, the integrity of the acrosome increased with the higher concentration of EY.
    UNASSIGNED: In conclusion, the post-thawed Hu ram semen diluted with a diluent containing 6% GLY and 20% EY exhibited higher quality compared to the other groups.
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  • 文章类型: Journal Article
    嵌入随机取向的大分子的玻璃化薄膜的形成是低温样品电子显微镜的必要先决条件。最常见的是,这是使用近40年前首次描述的骤降冷冻方法实现的。虽然这是一个强大的方法,不同大分子的行为在冻结时显示出很大的变化,并且通常需要进行优化以获得各向同性,高分辨率重建。对于这种薄膜中的大分子,在印迹和冷冻之间的时间内遇到空气-水界面并采用首选方向的可能性非常高。使用优先定向粒子的3D重建通常会导致各向异性和不可解释的映射。目前,这个普遍的问题没有通用的解决方案,但是已经尝试了几种主要集中在使用添加剂和新型网格修饰的样品制备上的方法。在这项研究中,通过对选定的研究良好的大分子进行分析,研究了物理和化学因素对大分子取向的影响,并揭示了确定蛋白质在低温EM网格上行为的重要参数。这些见解突出了导致优选取向的相互作用的性质,并且可用于系统地解决任何给定大分子的取向偏差,并提供设计小分子添加剂以增强样品稳定性和行为的框架。
    The formation of a vitrified thin film embedded with randomly oriented macromolecules is an essential prerequisite for cryogenic sample electron microscopy. Most commonly, this is achieved using the plunge-freeze method first described nearly 40 years ago. Although this is a robust method, the behaviour of different macromolecules shows great variation upon freezing and often needs to be optimized to obtain an isotropic, high-resolution reconstruction. For a macromolecule in such a film, the probability of encountering the air-water interface in the time between blotting and freezing and adopting preferred orientations is very high. 3D reconstruction using preferentially oriented particles often leads to anisotropic and uninterpretable maps. Currently, there are no general solutions to this prevalent issue, but several approaches largely focusing on sample preparation with the use of additives and novel grid modifications have been attempted. In this study, the effect of physical and chemical factors on the orientations of macromolecules was investigated through an analysis of selected well studied macromolecules, and important parameters that determine the behaviour of proteins on cryo-EM grids were revealed. These insights highlight the nature of the interactions that cause preferred orientations and can be utilized to systematically address orientation bias for any given macromolecule and to provide a framework to design small-molecule additives to enhance sample stability and behaviour.
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