BACKGROUND & AIMS: :The cytosolic fraction of Vigna radiata contains a 17-kD protein that binds plant hormones from the cytokinin group, such as zeatin. Using recombinant protein and isothermal titration calorimetry as well as fluorescence measurements coupled with ligand displacement, we have reexamined the K(d) values and show them to range from approximately 10(-6) M (for 4PU30) to 10(-4) M (for zeatin) for 1:1 stoichiometry complexes. In addition, we have crystallized this cytokinin-specific binding protein (Vr CSBP) in complex with zeatin and refined the structure to 1.2 A resolution. Structurally, Vr CSBP is similar to plant pathogenesis-related class 10 (PR-10) proteins, despite low sequence identity (<20%). This unusual fold conservation reinforces the notion that classic PR-10 proteins have evolved to bind small-molecule ligands. The fold consists of an antiparallel beta-sheet wrapped around a C-terminal alpha-helix, with two short alpha-helices closing a cavity formed within the protein core. In each of the four independent CSBP molecules, there is a zeatin ligand located deep in the cavity with conserved conformation and protein-ligand interactions. In three cases, an additional zeatin molecule is found in variable orientation but with excellent definition in electron density, which plugs the entrance to the binding pocket, sealing the inner molecule from contact with bulk solvent.

背景与目标： : Vigna radiata的胞质部分包含一种17 kD的蛋白质，该蛋白质结合细胞分裂素组的植物激素，例如玉米蛋白。使用重组蛋白和等温滴定量热法以及结合配体置换的荧光测量，我们已经重新检查了K(d) 值，并显示它们的范围从大约10(-6) M (对于4PU30) 到10(-4) M (对于玉米蛋白) 1:1化学计量复合物。此外，我们已经将这种细胞分裂素特异性结合蛋白 (Vr CSBP) 与玉米素复合物结晶，并细化结构以1.2分辨率。结构上，vrcsbp与植物发病机制相关的10类 (PR-10) 蛋白相似，尽管序列同一性低 (<20%)。这种不寻常的折叠保守性强化了经典PR-10蛋白已经进化成结合小分子配体的观念。折叠由包裹在C末端 α 螺旋周围的反平行 β 折叠组成，两个短的 α 螺旋封闭了蛋白质核心内形成的空腔。在四个独立的CSBP分子中的每一个中，都有一个玉米素配体位于腔深处，具有保守的构象和蛋白质-配体相互作用。在三种情况下，发现了一个附加的玉米蛋白分子，其取向可变，但电子密度具有极好的清晰度，从而堵塞了结合袋的入口，从而密封了内部分子，使其不与本体溶剂接触。

BACKGROUND & AIMS: :Structured RNAs play an essential role in chromosome maintenance, RNA processing, protein biosynthesis, and protein transport. To understand RNA function in these diverse biological systems, the rules for RNA folding and recognition must be learned. Recent crystal structures of hammerhead ribozymes, a group I intron domain, and RNA duplexes provide new insights into the principles of RNA folding and function.

背景与目标： : 结构化RNA在染色体维持，RNA加工，蛋白质生物合成和蛋白质转运中起着至关重要的作用。要了解这些不同生物系统中的RNA功能，必须学习RNA折叠和识别的规则。锤头核酶，I组内含子结构域和RNA双链体的最新晶体结构为RNA折叠和功能的原理提供了新的见解。

BACKGROUND & AIMS: :Botulinum neurotoxins (BoNTs) can cause paralysis at exceptionally low concentrations and include seven serotypes (BoNT/A-G). The chimeric BoNT/DC toxin has a receptor binding domain similar to the same region in BoNT/C. However, BoNT/DC does not share protein receptor with BoNT/C. Instead, it shares synaptotagmin (Syt) I and II as receptors with BoNT/B, despite their low sequence similarity. Here, we present the crystal structures of the binding domain of BoNT/DC in complex with the recognition domains of its protein receptors, Syt-I and Syt-II. The structures reveal that BoNT/DC possesses a Syt binding site, distinct from the established Syt-II binding site in BoNT/B. Structure-based mutagenesis further shows that hydrophobic interactions play a key role in Syt binding. The structures suggest that the BoNT/DC ganglioside binding sites are independent of the protein receptor binding site. Our results reveal the remarkable versatility in the receptor recognition of the BoNTs.

背景与目标： : 肉毒杆菌神经毒素 (BoNTs) 在极低的浓度下会导致瘫痪，包括七种血清型 (BoNT/A-G)。嵌合BoNT/DC毒素具有类似于BoNT/C中相同区域的受体结合结构域。但是，BoNT/DC与BoNT/C不共享蛋白质受体。相反，尽管它们的序列相似性较低，但它与BoNT/B共享突触标记蛋白 (Syt) I和II作为受体。在这里，我们介绍了BoNT/DC结合域的晶体结构与其蛋白质受体syt-i和syt-ii的识别域复合。结构表明，BoNT/DC具有Syt结合位点，与BoNT/B中已建立的Syt-II结合位点不同。基于结构的诱变进一步表明疏水相互作用在Syt结合中起关键作用。结构表明BoNT/DC神经节苷脂结合位点与蛋白受体结合位点无关。我们的结果揭示了BoNTs受体识别的显着多功能性。

BACKGROUND & AIMS: :The crystal structures of CsGST in two different space groups revealed that Asp26 and His79 coordinate a zinc ion. In one space group, His46 of an adjacent molecule participates in the coordination within 2.0Å. In the other space group, Asp26, His79 and a water molecule coordinate a zinc ion. The CsGST-D26H structure showed that four histidine residues - His26 and His79 from one molecule and the same residues from a symmetry-related neighboring molecule - coordinate a zinc ion. The coordinated zinc ions are located between two molecules and mediate molecular contacts within the crystal.

背景与目标： : CsGST在两个不同空间群中的晶体结构表明Asp26和His79配位锌离子。在一个空间群中，相邻分子的His46参与2.0内的配位。在另一个空间群中，Asp26，His79和一个水分子配位锌离子。CsGST-D26H结构表明，四个组氨酸残基-来自一个分子的His26和His79以及来自对称相关相邻分子的相同残基-配位锌离子。配位的锌离子位于两个分子之间，并在晶体内介导分子接触。

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。