BACKGROUND & AIMS: :The malonyl coenzyme A (CoA)-acyl carrier protein (ACP) transacylase (MCAT) plays a key role in cell wall biosynthesis in Mycobacterium tuberculosis and other bacteria. The M. tuberculosis MCAT (MtMCAT) is encoded by the FabD gene and catalyzes the transacylation of malonate from malonyl-CoA to holo-ACP. Malonyl-ACP is the substrate in fatty acid biosynthesis and is a by-product of the transacylation reaction. This ability for fatty acid biosynthesis enables M. tuberculosis to survive in hostile environments, and thus understanding the mechanism of biosynthesis is important for the design of new anti-tuberculosis drugs. The 2.3 A crystal structure of MtMCAT reported here shows that its catalytic mechanism differs from those of ScMCAT and EcMCAT, whose structures have previously been determined. In MtMCAT, the C(beta)-O(gamma) bond of Ser91 turns upwards, resulting in a different orientation and thus an overall change of the active pocket compared to other known MCAT enzymes. We identify three new nucleophilic attack chains from the MtMCAT structure: His90-Ser91, Asn155-Wat6-Ser91 and Asn155-His90-Ser91. Enzyme activity assays show that His90A, Asn155A and His90A-Asn155A mutants all have substantially reduced MCAT activity, indicating that M. tuberculosis MCAT supports a unique means of proton transfer. Furthermore, His194 cannot form part of a His-Ser catalytic dyad and only stabilizes the substrate. This new discovery should provide a deeper insight into the catalytic mechanisms of MCATs.

背景与目标： : 丙二酰辅酶a (CoA)-酰基载体蛋白 (ACP) 转酰基酶 (MCAT) 在结核分枝杆菌和其他细菌的细胞壁生物合成中起关键作用。结核分枝杆菌MCAT (MtMCAT) 由FabD基因编码，可催化丙二酸从丙二酰辅酶a转酰化为holo-ACP。丙二酰-ACP是脂肪酸生物合成中的底物，是转酰化反应的副产物。这种脂肪酸生物合成的能力使结核分枝杆菌能够在恶劣的环境中生存，因此了解生物合成的机理对于设计新的抗结核药物很重要。本文报道的MtMCAT的2.3 A晶体结构表明其催化机理不同于ScMCAT和EcMCAT的催化机理，ScMCAT和EcMCAT的结构先前已经确定。在MtMCAT中，与其他已知的MCAT酶相比，Ser91的C (β)-O (γ) 键向上旋转，导致不同的方向，从而导致活性口袋的整体变化。我们从MtMCAT结构中识别出三个新的亲核攻击链: His90-Ser91，Asn155-Wat6-Ser91和Asn155-His90-Ser91。酶活性测定表明His90A，Asn155A和His90A-Asn155A突变体均具有显着降低的MCAT活性，表明结核分枝杆菌MCAT支持质子转移的独特手段。此外，His194不能形成His-Ser催化二元体的一部分，只能稳定底物。这一新发现将为MCATs的催化机制提供更深入的了解。

BACKGROUND & AIMS: :Calmodulin (CaM) regulation of Ca(2+) channels is central to Ca(2+) signaling. Ca(V)1 versus Ca(V)2 classes of these channels exhibit divergent forms of regulation, potentially relating to customized CaM/IQ interactions among different channels. Here we report the crystal structures for the Ca(2+)/CaM IQ domains of both Ca(V)2.1 and Ca(V)2.3 channels. These highly similar structures emphasize that major CaM contacts with the IQ domain extend well upstream of traditional consensus residues. Surprisingly, upstream mutations strongly diminished Ca(V)2.1 regulation, whereas downstream perturbations had limited effects. Furthermore, our Ca(V)2 structures closely resemble published Ca(2+)/CaM-Ca(V)1.2 IQ structures, arguing against Ca(V)1/2 regulatory differences based solely on contrasting CaM/IQ conformations. Instead, alanine scanning of the Ca(V)2.1 IQ domain, combined with structure-based molecular simulation of corresponding CaM/IQ binding energy perturbations, suggests that the C lobe of CaM partially dislodges from the IQ element during channel regulation, allowing exposed IQ residues to trigger regulation via isoform-specific interactions with alternative channel regions.

背景与目标： 钙调蛋白 (CaM) 对Ca(2 +) 通道的调节是Ca(2 +) 信号传导的核心。这些通道的Ca(V)1与Ca(V)2类表现出不同的调节形式，可能与不同通道之间的定制CaM/IQ相互作用有关。在这里，我们报告Ca(V)2.1和Ca(V)2.3通道的Ca(2 +)/CaM IQ域的晶体结构。这些高度相似的结构强调，与IQ域的主要CaM接触在传统共有残基的上游延伸。令人惊讶的是，上游突变强烈地减少了Ca(V)2.1调节，而下游扰动具有有限的影响。此外，我们的Ca(V)2结构与公开的Ca(2 +)/CaM-Ca(V)1.2 IQ结构非常相似，仅基于对比的CaM/IQ构象反对Ca(V)1/2调节差异。相反，Ca(V)2.1 IQ域的丙氨酸扫描，结合相应CaM/IQ结合能扰动的基于结构的分子模拟，表明在通道调节过程中，CaM的C波瓣部分地从IQ元素中转移，允许暴露的IQ残基通过与其他通道区域的同工型特异性相互作用触发调节。

BACKGROUND & AIMS: :The annular single-crystal brain camera (ASPECT) is a digital SPECT system with a single-crystal sodium iodide thallium Nal(Tl) ring detector and collimator system designed to view the patient's head from three angles simultaneously. The ring is rotated concentrically to the detector for three-dimensional reconstruction over a 21.4 cm (diameter) by 10.7 cm (length) field of view. We evaluated the system clinically by imaging a Hoffman brain phantom and seven subjects, of whom two were normal controls, three had previous cerebral infarction and two had dementia. The ASPECT system produced tomographic images of high spatial resolution. In normal subjects, the separation of striata from thalami by the posterior limbs of the internal capsules was much clearer on ASPECT images than on rotating gamma camera images. The high spatial resolution obtained with the ASPECT system translates into superior anatomical representation of the brain compared to the standard rotating gamma camera.

背景与目标： : 环形单晶脑相机 (ASPECT) 是一种数字SPECT系统，带有单晶碘化钠铊 (Tl) 环检测器和准直器系统，旨在从三个角度同时观察患者的头部。环与检测器同心地旋转，以在21.4厘米 (直径) 上通过10.7厘米 (长度) 视场进行三维重建。我们通过对霍夫曼脑模型和7名受试者进行成像来对系统进行临床评估，其中2名是正常对照，3名先前患有脑梗塞，2名患有痴呆症。ASPECT系统产生了高空间分辨率的断层图像。在正常受试者中，内囊后肢的纹状体与丘脑的分离在方面图像上比在旋转的伽马相机图像上要清晰得多。与标准旋转伽马相机相比，使用ASPECT系统获得的高空间分辨率可转化为大脑的优越解剖表现。

BACKGROUND & AIMS: :P-type ATPases are ATP-powered ion pumps, classified into five subfamilies (PI-PV). Of these, PII-type ATPases, including Ca2+-ATPase, Na+,K+-ATPase and gastric H+,K+-ATPase, among others, have been the most intensively studied. Best understood structurally and biochemically is Ca2+-ATPase from sarcoplasmic reticulum of fast twitch skeletal muscle (sarco(endo)plasmic reticulum Ca2+-ATPase 1a, SERCA1a). Since publication of the first crystal structure in 2000, it has continuously been a source of excitement, as crystal structures for new reaction intermediates always show large structural changes. Crystal structures now exist for most of the reaction intermediates, almost covering the entire reaction cycle. This year the crystal structure of a missing link, the E1·Mg2+ state, finally appeared, bringing another surprise: bound sarcolipin (SLN). The current status of two other important PII-type ATPases, Na+,K+-ATPase and H+,K+-ATPase, is also briefly described.

背景与目标： : P型ATP酶是ATP驱动的离子泵，分为五个亚族 (PI-PV)。其中，PII型ATPase (包括Ca2-ATPase，Na，K-ATPase和胃H，K-ATPase等) 的研究最为深入。结构和生物化学上最好的理解是来自快速抽搐骨骼肌的肌浆网的Ca2-ATPase (sarco(endo) 浆网Ca2-ATPase 1a，SERCA1a)。自从第一个晶体结构2000年发表以来，它一直是一个令人兴奋的来源，因为新的反应中间体的晶体结构总是显示出较大的结构变化。现在，大多数反应中间体都存在晶体结构，几乎覆盖了整个反应周期。今年，一个缺失环节的晶体结构E1·Mg2 + 状态终于出现了，带来了另一个惊喜: 结合肌脂蛋白 (SLN)。还简要介绍了另外两种重要的PII型ATPase Na，K-ATPase和H，K-ATPase的当前状态。

BACKGROUND & AIMS: :Ultralente insulin has been one of the commercially most important insulin preparations in diabetes treatment over the last 50 years. It is a suspension of insulin microcrystals which dissolve slowly following subcutaneous injection. Because of the small crystal size of about 25 x 25 x 5 microm(3) the atomic structure has been elusive until now. Here we present the crystal structures from Ultralente and their precursor microcrystals from the industrial manufacturing process. During this process insulin undergoes a conformational change within the microcrystals. Both structures show canonical folding of the insulin molecules but exhibit a number of new features when compared with other insulin structures. Surprisingly, we found that the Ultralente crystals bind the conservation agent methylparaben, which slows down dissolution of the crystals and thus contributes to the long duration of action.

背景与目标： : 在过去的50年中，Ultralente胰岛素一直是糖尿病治疗中商业上最重要的胰岛素制剂之一。它是胰岛素微晶的悬浮液，在皮下注射后会缓慢溶解。由于晶体尺寸约为25x5 microm(3)，因此原子结构一直难以捉摸。在这里，我们介绍了Ultralente的晶体结构及其工业制造过程中的前体微晶。在此过程中，胰岛素在微晶内发生构象变化。两种结构均显示出胰岛素分子的典型折叠，但与其他胰岛素结构相比，表现出许多新功能。令人惊讶的是，我们发现超烯晶体与守恒剂对羟基苯甲酸甲酯结合，从而减慢了晶体的溶解，从而有助于作用的持续时间长。

BACKGROUND & AIMS: BACKGROUND:EstE1 is a hyperthermophilic esterase belonging to the hormone-sensitive lipase family and was originally isolated by functional screening of a metagenomic library constructed from a thermal environmental sample. Dimers and oligomers may have been evolutionally selected in thermophiles because intersubunit interactions can confer thermostability on the proteins. The molecular mechanisms of thermostabilization of this extremely thermostable esterase are not well understood due to the lack of structural information. RESULTS:Here we report for the first time the 2.1-A resolution crystal structure of EstE1. The three-dimensional structure of EstE1 exhibits a classic alpha/beta hydrolase fold with a central parallel-stranded beta sheet surrounded by alpha helices on both sides. The residues Ser154, Asp251, and His281 form the catalytic triad motif commonly found in other alpha/beta hydrolases. EstE1 exists as a dimer that is formed by hydrophobic interactions and salt bridges. Circular dichroism spectroscopy and heat inactivation kinetic analysis of EstE1 mutants, which were generated by structure-based site-directed mutagenesis of amino acid residues participating in EstE1 dimerization, revealed that hydrophobic interactions through Val274 and Phe276 on the beta8 strand of each monomer play a major role in the dimerization of EstE1. In contrast, the intermolecular salt bridges contribute less significantly to the dimerization and thermostability of EstE1. CONCLUSION:Our results suggest that intermolecular hydrophobic interactions are essential for the hyperthermostability of EstE1. The molecular mechanism that allows EstE1 to endure high temperature will provide guideline for rational design of a thermostable esterase/lipase using the lipolytic enzymes showing structural similarity to EstE1.

背景与目标：

BACKGROUND & AIMS: :The process of crystallization is often understood in terms of the fundamental microstructural elements of the crystallite being formed, such as surface orientation or the presence of defects. Considerably less is known about the role of the liquid structure on the kinetics of crystal growth. Here atomistic simulations and machine learning methods are employed together to demonstrate that the liquid adjacent to solid-liquid interfaces presents significant structural ordering, which effectively reduces the mobility of atoms and slows down the crystallization kinetics. Through detailed studies of silicon and copper we discover that the extent to which liquid mobility is affected by interface-induced ordering (IIO) varies greatly with the degree of ordering and nature of the adjacent interface. Physical mechanisms behind the IIO anisotropy are explained and it is demonstrated that incorporation of this effect on a physically-motivated crystal growth model enables the quantitative prediction of the growth rate temperature dependence.

背景与目标： : 结晶过程通常是根据所形成的微晶的基本微结构元素来理解的，例如表面取向或缺陷的存在。关于液体结构对晶体生长动力学的作用知之甚少。在这里，原子模拟和机器学习方法一起使用，以证明与固液界面相邻的液体具有明显的结构有序性，从而有效地降低了原子的迁移率并减慢了结晶动力学。通过对硅和铜的详细研究，我们发现，界面诱导有序 (IIO) 对液体迁移率的影响程度随相邻界面的有序程度和性质而变化很大。解释了IIO各向异性背后的物理机制，并证明了将这种效应纳入物理驱动的晶体生长模型可以定量预测生长速率温度依赖性。

BACKGROUND & AIMS: :We describe five cases of tumoral calcium pyrophosphate dihydrate crystal deposition disease (CPPDCD) and discuss the clinical, radiological and pathological features. Patients included 4 males and 1 female, ranging in age from 49 to 70 years (median, 63 yrs). The wrist was involved in two patients. The thumb, palmar aspect of the proximal phalanx of the middle finger and dorsum of the carpal bone of the hand were involved in one patient each. In one patient, a preoperative diagnosis of chondrosarcoma had been made. Macroscopically, the lesion was a circumscribed whitish-gray mass with a more or less chalky appearance, measuring between 1.0 to 6.2 cm (median, 2.5 cm). Histologically, all five lesions contained areas of calcification with crystal deposits and chondroid metaplasia. The majority of crystals were rhomboid in shape, characteristic of CPPD, but some needle-shaped crystals were also identified, which resembled urate crystals. A review of the 54 reported cases of tumoral CPPDCD including our series indicated that they could be divided into two categories based on anatomic location: central (head and neck) type (n = 33) and distal (extremity) type (n = 21). Patients of these two groups were not different with respect to age and gender, but those with the central type often presented with a painful mass (15 patients, 46%), or neurological disturbances (11 patients, 33%). Patients with the distal type presented with a painless mass or swelling (12 patients, 57%), but none had neurological signs, although 8 (38.1%) presented with acute attack similar to tophaceous gout. Tumoral CP-PDCD should be differentiated from tophaceous gout, tumoral calcinosis, and malignant or benign tumors.

背景与目标： : 我们描述了5例肿瘤焦磷酸钙二水合物晶体沉积病 (CPPDCD)，并讨论了临床，影像学和病理特征。患者包括4名男性和1名女性，年龄从49岁到70岁 (中位数为63岁)。手腕涉及两名患者。一名患者分别涉及拇指，中指近端指骨的手掌和手部腕骨的背。在一名患者中，已进行了软骨肉瘤的术前诊断。从宏观上看，病变是外接的白色灰色肿块，其外观或多或少呈白垩状，介于1.0至6.2厘米之间 (中位数为2.5厘米)。从组织学上讲，所有五个病变都包含有晶体沉积和软骨化生的钙化区域。大多数晶体为菱形，具有CPPD的特征，但也发现了一些针状晶体，类似于尿酸盐晶体。对包括我们系列在内的54例报告的肿瘤CPPDCD病例的回顾表明，根据解剖位置，它们可以分为两类: 中央 (头部和颈部) 类型 (n = 33) 和远端 (四肢) 类型 (n = 21)。这两组患者在年龄和性别方面没有差异，但中枢型患者通常表现为疼痛性肿块 (15例，46%) 或神经系统疾病 (11例，33%)。远端型患者表现为无痛性肿块或肿胀 (12例，57% 例)，但没有神经系统体征，尽管8例 (38.1% 例) 表现为类似于痛风的急性发作。肿瘤性cp-pdcd应与痛风，肿瘤性钙质沉着症和恶性或良性肿瘤区分开。

BACKGROUND & AIMS: :Gas sensors are important in many fields such as environmental monitoring, agricultural production, public safety, and medical diagnostics. Herein, Tamm plasmon resonance in a photonic bandgap is used to develop an optical gas sensor with high performance. The structure of the proposed sensor comprises a gas cavity sandwiched between a one-dimensional porous silicon photonic crystal and an Ag layer deposited on a prism. The optimised structure of the proposed sensor achieves ultra-high sensitivity (S = 1.9×105 nm/RIU) and a low detection limit (DL = 1.4×10-7 RIU) compared to the existing gas sensor. The brilliant sensing performance and simple design of the proposed structure make our device highly suitable for use as a sensor in a variety of biomedical and industrial applications.

背景与目标： : 气体传感器在环境监测，农业生产，公共安全和医疗诊断等许多领域都很重要。本文使用光子带隙中的Tamm等离子体共振来开发具有高性能的光学气体传感器。所提出的传感器的结构包括夹在一维多孔硅光子晶体和沉积在棱镜上的Ag层之间的气体腔。与现有气体传感器相比，所提出的传感器的优化结构实现了超高灵敏度 (s   =   1.9 × 105  nm/RIU) 和低检测限 (dl   =   1.4 × 10-7 RIU)。所提出的结构的出色传感性能和简单的设计使我们的设备非常适合在各种生物医学和工业应用中用作传感器。

BACKGROUND & AIMS: :We describe the crystallization and structure determination of the 30 S ribosomal subunit from Thermus thermophilus. Previous reports of crystals that diffracted to 10 A resolution were used as a starting point to improve the quality of the diffraction. Eventually, ideas such as the addition of substrates or factors to eliminate conformational heterogeneity proved less important than attention to detail in yielding crystals that diffracted beyond 3 A resolution. Despite improvements in technology and methodology in the last decade, the structure determination of the 30 S subunit presented some very challenging technical problems because of the size of the asymmetric unit, crystal variability and sensitivity to radiation damage. Some steps that were useful for determination of the atomic structure were: the use of anomalous scattering from the LIII edges of osmium and lutetium to obtain the necessary phasing signal; the use of tunable, third-generation synchrotron sources to obtain data of reasonable quality at high resolution; collection of derivative data precisely about a mirror plane to preserve small anomalous differences between Bijvoet mates despite extensive radiation damage and multi-crystal scaling; the pre-screening of crystals to ensure quality, isomorphism and the efficient use of scarce third-generation synchrotron time; pre-incubation of crystals in cobalt hexaammine to ensure isomorphism with other derivatives; and finally, the placement of proteins whose structures had been previously solved in isolation, in conjunction with biochemical data on protein-RNA interactions, to map out the architecture of the 30 S subunit prior to the construction of a detailed atomic-resolution model.

背景与目标： : 我们描述了嗜热热热菌30 s核糖体亚基的结晶和结构测定。先前关于衍射至10 A分辨率的晶体的报道被用作提高衍射质量的起点。最终，在产生衍射超过3 A分辨率的晶体时，诸如添加底物或消除构象异质性的因素之类的想法被证明不如关注细节重要。尽管在过去十年中技术和方法有所改进，但由于不对称单元的大小，晶体可变性和对辐射损伤的敏感性，30 s亚基的结构确定提出了一些非常具有挑战性的技术问题。对确定原子结构有用的一些步骤是: 使用锇和镥的LIII边缘的异常散射来获得必要的定相信号; 使用可调谐的第三代同步加速器源来获得高分辨率的合理质量的数据; 精确收集关于镜像平面的衍生数据，以保持Bijvoet mate之间的微小异常差异，尽管存在广泛的辐射损伤和多晶体缩放; 晶体的预筛选，以确保质量、同构和有效利用稀缺的第三代同步加速器时间; 晶体在六氨合钴中预孵育，以确保与其他衍生物的同构; 最后，结合蛋白质-RNA相互作用的生化数据，将其结构先前已被隔离解决的蛋白质放置，在构建详细的原子分辨率模型之前，绘制出30 s子单元的体系结构。

BACKGROUND & AIMS: :The optimization of aqueous solubility is an important step along the route to bringing a new therapeutic to market. We describe the development of an empirical computational model to rank the pH-dependent aqueous solubility of drug candidates. The model consists of three core components to describe aqueous solubility. The first is a multivariate QSAR model for the prediction of the intrinsic solubility of the neutral solute. The second facet of the approach is the consideration of ionization using a predicted pKa and the Henderson-Hasselbalch equation. The third aspect of the model is a novel method for assessing the effects of crystal packing on solubility through a series of short molecular dynamics simulations of an actual or hypothetical small molecule crystal structure at escalating temperatures. The model also includes a Monte Carlo error function that considers the variability of each of the underlying components of the model to estimate the 90% confidence interval of estimation.

背景与目标： : 水溶性的优化是将新的治疗方法推向市场的重要一步。我们描述了经验计算模型的开发，以对候选药物的pH依赖性水溶性进行排名。该模型由三个核心组件组成，用于描述水溶性。首先是用于预测中性溶质固有溶解度的多元QSAR模型。该方法的第二个方面是使用预测的pKa和Henderson-Hasselbalch方程来考虑电离。该模型的第三方面是一种新颖的方法，用于通过在升高的温度下对实际或假设的小分子晶体结构进行一系列简短的分子动力学模拟来评估晶体堆积对溶解度的影响。该模型还包括蒙特卡洛误差函数，其考虑模型的基础组件中的每一个的可变性以估计估计的90% 置信区间。

BACKGROUND & AIMS: :The rainbow trapping effect has been demonstrated in electromagnetic and acoustic waves. In this study, rainbow trapping of ultrasonic guided waves is achieved in chirped phononic crystal plates that spatially modulate the dispersion, group velocity, and stopband. The rainbow trapping is related to the progressively slowing group velocity, and the extremely low group velocity near the lower boundary of a stopband that gradually varies in chirped phononic crystal plates. As guided waves propagate along the phononic crystal plate, waves gradually slow down and finally stop forward propagating. The energy of guided waves is concentrated at the low velocity region near the stopband. Moreover, the guided wave energy of different frequencies is concentrated at different locations, which manifests as rainbow guided waves. We believe implementing the rainbow trapping will open new paradigms for guiding and focusing of guided waves. Moreover, the rainbow guided waves with energy concentration and spatial separation of frequencies may have potential applications in nondestructive evaluation, spatial wave filtering, energy harvesting, and acoustofluidics.

背景与目标： : 彩虹诱捕效应已在电磁波和声波中得到证明。在这项研究中，在chi声子晶体板上实现了超声波导波的彩虹俘获，该晶体板在空间上调制了色散，群速度和阻带。彩虹陷阱与逐渐减慢的群速度以及在chi声子晶体板中逐渐变化的阻带下边界附近的极低群速度有关。随着导波沿着声子晶体板传播，波逐渐变慢，最后停止向前传播。导波的能量集中在阻带附近的低速区域。而且，不同频率的导波能量集中在不同的位置，表现为彩虹导波。我们相信实施彩虹诱捕将为引导和聚焦导波开辟新的范例。此外，具有能量集中和频率空间分离的彩虹导波可能在无损评估，空间波过滤，能量收集和声流学中具有潜在的应用。

BACKGROUND & AIMS: :Recently, expired gases are analyzed non-invasively for monitoring the substances in the blood. Breath ammonia has been shown to correlate with BUN (blood urea nitrogen) and Cr (creatinine), both of which are indicators of solute removal in hemodialysis. In this study, breath ammonia concentration was continuously measured using a crystal oscillator QCM (quartz crystal microbalance) during the expiration of patients undergoing dialysis treatment. The results show that NH3 (ammonia) decreased gradually as the treatment proceeded. A strong correlation was observed between changes in the frequency of the QCM gas sensor and both the pre-dialysis BUN level (r=0.71, p<0.05) and the post-dialysis BUN level (r=0.90, p<0.05). NH3 was found to fall precipitously during dialysis. The differences were statistically significant. In addition, we found a statistically significant correlation between BUN and NH3 in expired gas. These results suggest that continuous measurement of NH3 is useful to assess the status of solute removal during hemodialysis.

背景与目标： : 最近，对呼出气体进行了非侵入性分析，以监测血液中的物质。呼吸氨已被证明与BUN (血尿素氮) 和Cr (肌酐) 相关，这两者都是血液透析中溶质去除的指标。在这项研究中，在接受透析治疗的患者呼气期间，使用晶体振荡器QCM (石英晶体微量天平) 连续测量呼吸氨浓度。结果表明，随着处理的进行，NH3 (氨) 逐渐降低。观察到QCM气体传感器的频率变化与透析前BUN水平 (r = 0.71，p<0.05) 和透析后BUN水平 (r = 0.90，p<0.05) 之间的强相关性。在透析过程中发现NH3急剧下降。差异有统计学意义。此外，我们发现呼出气体中BUN和NH3之间存在统计学上的显着相关性。这些结果表明，连续测量NH3可用于评估血液透析过程中溶质去除的状态。

BACKGROUND & AIMS: :DNA mismatch repair ensures genomic integrity on DNA replication. Recognition of a DNA mismatch by a dimeric MutS protein initiates a cascade of reactions and results in repair of the newly synthesized strand; however, details of the molecular mechanism remain controversial. Here we present the crystal structure at 2.2 A of MutS from Escherichia coli bound to a G x T mismatch. The two MutS monomers have different conformations and form a heterodimer at the structural level. Only one monomer recognizes the mismatch specifically and has ADP bound. Mismatch recognition occurs by extensive minor groove interactions causing unusual base pairing and kinking of the DNA. Nonspecific major groove DNA-binding domains from both monomers embrace the DNA in a clamp-like structure. The interleaved nucleotide-binding sites are located far from the DNA. Mutations in human MutS alpha (MSH2/MSH6) that lead to hereditary predisposition for cancer, such as hereditary non-polyposis colorectal cancer, can be mapped to this crystal structure.

背景与目标： : DNA错配修复确保DNA复制的基因组完整性。二聚体MutS蛋白对DNA错配的识别会引发一系列反应，并导致新合成链的修复; 然而，分子机制的细节仍存在争议。在这里，我们给出了与G x T错配结合的来自大肠杆菌的MutS的2.2 A处的晶体结构。两种MutS单体具有不同的构象，在结构水平上形成异二聚体。只有一种单体可以特异性识别错配，并具有ADP结合。错配识别是由广泛的微小沟槽相互作用引起的，从而导致异常的碱基配对和DNA扭结。来自两种单体的非特异性主要凹槽DNA结合结构域以钳形结构包围DNA。交错的核苷酸结合位点位于远离DNA的位置。人类MutS α (MSH2/MSH6) 的突变可导致遗传性癌症易感性，例如遗传性非息肉病性结直肠癌，可映射到该晶体结构。

BACKGROUND & AIMS: :Two cysteine proteinase inhibitors from cowpea, VuCys1 and VuCys2, were produced in E. coli ArcticExpress (DE3). The recombinant products strongly inhibited papain and chymopapain as well as the midgut proteases from Callosobruchus maculatus larvae, a bruchid that uses cysteine proteases as major digestive enzymes. Heat treatment at 100°C for up to 60min or incubation at various pH values caused little reduction in the papain inhibitory activity of both inhibitors. Moreover, minor conformational variations, as probed by circular dichroism spectroscopy, were observed after VuCys1 and VuCys2 were subjected to these treatments. The crystal structure of VuCys1 was determined at a resolution of 1.95Å, revealing a domain-swapped dimer in the asymmetric unit. However, the two lobes of the domain-swapped dimer are positioned closer to each other in VuCys1 in comparison to other similar cystatin structures. Moreover, some polar residues from opposite lobes recruit water molecules, forming a hydrogen bond network that mediates contacts between the lobes, thus generating an extended open interface. Due to the closer distance between the lobes, a small hydrophobic core is also formed, further stabilizing the folded domain-swapped dimer. These structural features might account for the extraordinary thermal and pH stability of VuCys1.

背景与目标： : 在大肠杆菌ArcticExpress (DE3) 中产生了两种来自cow豆的半胱氨酸蛋白酶抑制剂VuCys1和VuCys2。重组产品强烈抑制木瓜蛋白酶和木瓜蛋白酶以及callobruchus maculatus幼虫的中肠蛋白酶，callobruchus maculatus幼虫是一种使用半胱氨酸蛋白酶作为主要消化酶的bruchid。在100 °C下热处理达60分钟或在各种ph值下孵育几乎不会降低两种抑制剂的木瓜蛋白酶抑制活性。此外，在对VuCys1和VuCys2进行这些处理后，观察到了较小的构象变化，如通过圆二色光谱探测到的。以1.95的分辨率确定了VuCys1的晶体结构，揭示了不对称单元中的域交换二聚体。然而，与其他类似的胱抑素结构相比，域交换二聚体的两个叶在VuCys1中彼此靠近。此外，来自相反叶片的一些极性残基会募集水分子，形成氢键网络，介导叶片之间的接触，从而产生扩展的开放界面。由于裂片之间的距离更近，还形成了一个小的疏水核，从而进一步稳定了折叠的结构域交换的二聚体。这些结构特征可能解释了vucys1的非凡的热稳定性和pH稳定性。