BACKGROUND & AIMS: -2

背景与目标： -2

BACKGROUND & AIMS: DiSSU1 is an optional group I twintron present in the nuclear extrachromosomal ribosomal DNA of the myxomycete Didymium iridis. DiSSU1 appears to be complex both in structure and function. At the RNA level it has a twin-ribozyme organization composed of two group I ribozymes with different functions, separated by an open reading frame. Here, we show that DiSSU1 is mobile when haploid intron-containing and intron-less amoebae are mated. The mobility process is fast, being completed in 5-10 nuclear cycles after mating in the developing zygote and plasmodia. Analyses of progeny from genetic crosses confirm intron mobility. DiSSU1 is the first example of a mobile group I twintron. The intron-encoded protein was expressed in Escherichia coli and found to be an endonuclease, I-DirI, that cleaves an intron-less ribosomal DNA allele at the intron-insertion site, and is probably involved in intron homing. The endonuclease I-DirI seems to be a rare example of a protein that is expressed from a ribozyme-processed RNA polymerase I transcript in vivo.

背景与目标： DiSSU1是一种可选的I族双冠子，存在于粘菌素二钕虹膜的核染色体外核糖体DNA中。DiSSU1在结构和功能上似乎都很复杂。在RNA水平上，它具有一个双核酶组织，该组织由两个具有不同功能的I族核酶组成，并由开放阅读框隔开。在这里，我们表明，当单倍体内含子和无内含子的阿米巴交配时，DiSSU1是可移动的。迁移率过程很快，在发育中的合子和疟原虫交配后，在5-10个核循环中完成。对遗传杂交后代的分析证实了内含子的迁移率。DiSSU1是移动组I twintron的第一个示例。内含子编码的蛋白在大肠杆菌中表达，发现它是一种内切核酸酶I-DirI，在内含子插入位点切割无内含子核糖体DNA等位基因，并且可能参与内含子归巢。核酸内切酶I-DirI似乎是从核酶处理的RNA聚合酶I转录本体内表达的蛋白质的罕见例子。

BACKGROUND & AIMS: The mammalian transcription factor LSF (CP2/LBP-1c) binds cellular promoters modulated by cell growth signals. We demonstrate here that LSF-DNA-binding activity is strikingly regulated by induction of cell growth in human peripheral T lymphocytes. Within 15 min of mitogenic stimulation of these cells, the level of LSF-DNA-binding activity increased by a factor of five. The level of LSF protein in the nucleus remained constant throughout this interval. However, a rapid decrease in the electrophoretic mobility of LSF, attributable to phosphorylation, correlated with the increase in DNA-binding activity. pp44 (ERK1) phosphorylated LSF in vitro on the same residue that was phosphorylated in vivo, specifically at amino acid position 291, as indicated by mutant analysis. As direct verification of the causal relationship between phosphorylation and DNA-binding activity, treatment in vitro of LSF with phosphatase both increased the electrophoretic mobility of the protein and decreased LSF-DNA-binding activity. This modulation of LSF-DNA-binding activity as T cells progress from a resting to a replicating state reveals that LSF activity is regulated during cell growth and suggests that LSF regulates growth-responsive promoters.

背景与目标： 哺乳动物转录因子LSF (CP2/LBP-1c) 结合由细胞生长信号调节的细胞启动子。我们在此证明，LSF-DNA结合活性通过诱导人外周血T淋巴细胞中的细胞生长而显着调节。在有丝分裂刺激这些细胞的15分钟内，lsf-dna结合活性水平增加了5倍。在整个间隔内，细胞核中LSF蛋白的水平保持恒定。然而，由于磷酸化，LSF的电泳迁移率迅速降低与DNA结合活性的增加有关。pp44 (ERK1) 在体内磷酸化的相同残基上体外磷酸化LSF，具体地在氨基酸位置291，如突变体分析所示。作为磷酸化与DNA结合活性之间因果关系的直接验证，用磷酸酶体外处理LSF既增加了蛋白质的电泳迁移率，又降低了LSF-DNA结合活性。随着T细胞从静止状态发展为复制状态，LSF-DNA结合活性的这种调节表明LSF活性在细胞生长过程中受到调节，并表明LSF调节生长反应性启动子。

BACKGROUND & AIMS: Modelling and calculations are presented as a first step towards mechanistic interpretation and prediction of radiation effects based on the spectrum of initial DNA damage produced by low energy electrons (100 eV-4.5 keV) that can be compared with experimental information. Relative yields of single and clustered strand breaks are presented in terms of complexity and source of damage, either by direct energy deposition or by reaction of OH radicals, and dependence on the activation probability of OH radicals and the amount of energy required to give a single strand break (ssb). Data show that the majority of interactions in DNA do not lead to damage in the form of strand breaks and when they do occur, they are most frequently simple ssb. However, for double-strand breaks (dsb), a high proportion (approximately 30%) are of more complex forms, even without considering additional complexity from base damage. The greater contribution is from direct interactions in the DNA but reactions of OH radicals add substantially to this, both in terms of the total number of breaks and in increasing the complexity within a cluster. It has been shown that the lengths of damaged segments of DNA from individual electron tracks tend to be short, indicating that consequent deletion length (simply by loss of a fragment between nearby dsb) would be short, very seldom exceeding a few tens of base pairs.

背景与目标： 建模和计算是基于低能电子 (100 eV-4.5 keV) 产生的初始DNA损伤谱的辐射效应的机械解释和预测的第一步，可以与实验信息进行比较。通过直接能量沉积或OH自由基的反应，以及对OH自由基的激活概率和产生所需能量的依赖，以复杂性和损伤来源表示单链断裂 (ssb)。数据表明，DNA中的大多数相互作用不会以链断裂的形式导致损伤，当它们发生时，它们最常见的是简单的ssb。然而，对于双链断裂 (dsb)，高比例 (约30%) 是更复杂的形式，甚至不考虑来自基础损伤的额外复杂性。更大的贡献来自DNA中的直接相互作用，但是OH自由基的反应在断裂总数和增加簇内的复杂性方面都大大增加了这一点。已经表明，来自单个电子轨道的DNA受损片段的长度往往很短，这表明随之而来的缺失长度 (仅通过附近dsb之间的片段丢失) 将很短，很少超过几十个碱基对。

BACKGROUND & AIMS: :Streptococcus pneumoniae colonizes the human upper respiratory tract, and this asymptomatic colonization is known to precede pneumococcal disease. In this report, chemically defined and semisynthetic media were used to identify the initial steps of biofilm formation by pneumococcus during growth on abiotic surfaces such as polystyrene or glass. Unencapsulated pneumococci adhered to abiotic surfaces and formed a three-dimensional structure about 25 microm deep, as observed by confocal laser scanning microscopy and low-temperature scanning electron microscopy. Choline residues of cell wall teichoic acids were found to play a fundamental role in pneumococcal biofilm development. The role in biofilm formation of choline-binding proteins, which anchor to the teichoic acids of the cell envelope, was determined using unambiguously characterized mutants. The results showed that LytA amidase, LytC lysozyme, LytB glucosaminidase, CbpA adhesin, PcpA putative adhesin, and PspA (pneumococcal surface protein A) mutants had a decreased capacity to form biofilms, whereas no such reduction was observed in Pce phosphocholinesterase or CbpD putative amidase mutants. Moreover, encapsulated, clinical pneumococcal isolates were impaired in their capacity to form biofilms. In addition, a role for extracellular DNA and proteins in the establishment of S. pneumoniae biofilms was demonstrated. Taken together, these observations provide information on conditions that favor the sessile mode of growth by S. pneumoniae. The experimental approach described here should facilitate the study of bacterial genes that are required for biofilm formation. Those results, in turn, may provide insight into strategies to prevent pneumococcal colonization of its human host.

背景与目标： : 肺炎链球菌定植于人的上呼吸道，已知这种无症状的定植先于肺炎球菌疾病。在此报告中，使用化学定义的半合成介质来识别肺炎球菌在非生物表面 (例如聚苯乙烯或玻璃) 上生长过程中形成生物膜的初始步骤。未包封的肺炎球菌粘附在非生物表面，并形成约25微米深的三维结构，如共聚焦激光扫描显微镜和低温扫描电子显微镜观察到的。发现细胞壁磷壁酸的胆碱残基在肺炎球菌生物膜的发育中起基本作用。使用明确表征的突变体确定了锚定在细胞包膜的磷壁酸上的胆碱结合蛋白在生物膜形成中的作用。结果表明，LytA酰胺酶，LytC溶菌酶，LytB氨基葡萄糖苷酶，CbpA粘附素，PcpA假定粘附素和PspA (肺炎球菌表面蛋白A) 突变体形成生物膜的能力降低，而在Pce磷酸胆碱酯酶中未观察到这种降低或CbpD推定的酰胺酶突变体。此外，封装的临床肺炎球菌分离株形成生物膜的能力受到损害。此外，还证实了细胞外DNA和蛋白质在肺炎链球菌生物膜建立中的作用。综上所述，这些观察结果提供了有关有利于肺炎链球菌无柄生长方式的条件的信息。此处描述的实验方法应有助于研究生物膜形成所需的细菌基因。反过来，这些结果可以提供有关预防人类宿主肺炎球菌定植的策略的见解。

BACKGROUND & AIMS: We studied changes in glutamate receptors, expression of immediate early genes, and AP-1 DNA binding activity in the brains of phenobarbital (PB)-dependent and -withdrawn rats to investigate the possible involvement of activation of glutamate receptors in PB withdrawal syndrome. PB-dependent rats were prepared by feeding drug-admixed food for 5 weeks. Autoradiographic analysis showed that binding of [3H(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imin e (MK-801), an antagonist of N-methyl-D-aspartic acid (NMDA) receptors, increased significantly in the cerebral cortices of PB-dependent and 24-h-withdrawn rats. However, [3H]MK-801 binding in the hippocampus and [3H]6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and [3H]kainic acid binding in the hippocampus and cerebral cortex were essentially unchanged in both groups. PB withdrawal seizures were followed by increased expression of c-fos mRNA in the hippocampus and cerebral cortex and of c-jun mRNA in the cerebral cortex. The induction of c-fos and c-jun mRNA was suppressed by administration of MK-801. Furthermore, PB withdrawal enhanced AP-1 DNA binding activity in the brain. The present findings suggest functional enhancement of glutamatergic neurotransmission during the development of PB withdrawal syndrome.

背景与目标： 我们研究了苯巴比妥 (PB) 依赖性和退缩大鼠大脑中谷氨酸受体的变化，即刻早期基因的表达以及AP-1的DNA结合活性，以研究谷氨酸受体激活在PB戒断综合征中的可能参与。通过喂养混合药物的食物5周制备PB依赖性大鼠。放射自显影分析显示，N-甲基-d-天冬氨酸 (NMDA) 受体拮抗剂 [3H(+)-5-甲基-10,11-二氢-5H-二苯并 [a，D] cyclohepten-5，10-敏e (MK-801) 的结合，PB依赖性和24h撤回大鼠的大脑皮层显着增加。然而，[3h] MK-801在海马和 [3H]6-氰基-7-硝基喹喔啉-2结合，海马和大脑皮层中的3-二酮 (CNQX) 和 [3H] 海藻酸结合在两组中基本上没有变化。铅戒断发作后，海马和大脑皮层中c-fos mRNA的表达增加，大脑皮层中c-6月mRNA的表达增加。诱导c-MK-801可抑制fos和c-6月mRNA。此外，铅戒断增强了大脑中的AP-1 DNA结合活性。目前的发现表明，在铅戒断综合征的发展过程中，谷氨酸能神经传递的功能增强。

BACKGROUND & AIMS: The GATA family of vertebrate DNA binding regulatory proteins are expressed in diverse tissues and at different times of development. However, the DNA binding regions of these proteins possess considerable homology and recognize a rather similar range of DNA sequence motifs. DNA binding is mediated through two domains, each containing a zinc finger. Previous results have led to the conclusion that although in some cases the N-terminal finger can contribute to specificity and strength of binding, it does not bind independently, whereas the C-terminal finger is both necessary and sufficient for binding. Here we show that although this is true for the N-terminal finger of GATA-1, those of GATA-2 and GATA-3 are capable of strong independent binding with a preference for the motif GATC. Binding requires the presence of two basic regions located on either side of the N-terminal finger. The absence of one of these near the GATA-1 N-terminal finger probably accounts for its inability to bind. The combination of a single finger and two basic regions is a new variant of a motif that has been previously found in the binding domains of other finger proteins. Our results suggest that the DNA binding properties of the N-terminal finger may help distinguish GATA-2 and GATA-3 from GATA-1 and the other GATA family members in their selective regulatory roles in vivo.

背景与目标： 脊椎动物DNA结合调节蛋白的GATA家族在不同的组织和发育的不同时间表达。但是，这些蛋白质的DNA结合区域具有相当大的同源性，并且可以识别相当相似范围的DNA序列基序。DNA结合通过两个结构域介导，每个结构域都包含一个锌指。先前的结果得出的结论是，尽管在某些情况下，N末端手指可以促进特异性和结合强度，但它不会独立结合，而C末端手指对于结合既必要又足够。在这里，我们表明，尽管对于GATA-1的N末端手指是正确的，但GATA-2和GATA-3的手指能够强烈独立结合，并且偏爱基序GATC。结合需要存在位于N末端手指两侧的两个基本区域。在GATA-1的N末端手指附近没有这些手指之一可能是其无法结合的原因。单个手指和两个基本区域的组合是基序的新变体，以前已在其他手指蛋白的结合域中发现。我们的结果表明，N末端手指的DNA结合特性可能有助于将GATA-2和GATA-3与GATA-1和其他GATA家族成员在体内的选择性调节作用区分开。

BACKGROUND & AIMS: :Comparative genomics, using the model organism approach, has provided powerful insights into the structure and evolution of whole genomes. Unfortunately, only a small fraction of Earth's biodiversity will have its genome sequenced in the foreseeable future. Most wild organisms have radically different life histories and evolutionary genomics than current model systems. A novel technique is needed to expand comparative genomics to a wider range of organisms. Here, we describe a novel approach using an anonymous DNA microarray platform that gathers genomic samples of sequence variation from any organism. Oligonucleotide probe sequences placed on a custom 44 K array were 25 bp long and designed using a simple set of criteria to maximize their complexity and dispersion in sequence probability space. Using whole genomic samples from three known genomes (mouse, rat and human) and one unknown (Gonystylus bancanus), we demonstrate and validate its power, reliability, transitivity and sensitivity. Using two separate statistical analyses, a large numbers of genomic 'indicator' probes were discovered. The construction of a genomic signature database based upon this technique would allow virtual comparisons and simple queries could generate optimal subsets of markers to be used in large-scale assays, using simple downstream techniques. Biologists from a wide range of fields, studying almost any organism, could efficiently perform genomic comparisons, at potentially any phylogenetic level after performing a small number of standardized DNA microarray hybridizations. Possibilities for refining and expanding the approach are discussed.

背景与目标： : 使用模式生物方法的比较基因组学为整个基因组的结构和进化提供了有力的见解。不幸的是，在可预见的将来，地球生物多样性中只有一小部分将对其基因组进行测序。大多数野生生物的生活史和进化基因组学与当前的模型系统完全不同。需要一种新技术来将比较基因组学扩展到更广泛的生物体。在这里，我们描述了一种使用匿名DNA微阵列平台的新颖方法，该平台收集来自任何生物的序列变异的基因组样本。放置在定制的44 K阵列上的寡核苷酸探针序列长25 bp，并使用一组简单的标准进行设计，以最大程度地提高其在序列概率空间中的复杂性和分散性。使用来自三个已知基因组 (小鼠，大鼠和人类) 和一个未知基因组 (Gonystylus bancanus) 的全基因组样本，我们证明并验证了其功能，可靠性，传递性和敏感性。使用两个单独的统计分析，发现了大量的基因组 “指标” 探针。基于该技术的基因组签名数据库的构建将允许虚拟比较，并且简单的查询可以使用简单的下游技术生成用于大规模测定的最佳标记子集。来自广泛领域的生物学家，研究几乎任何生物，可以在进行少量标准化DNA微阵列杂交后，在潜在的任何系统发育水平上有效地进行基因组比较。讨论了改进和扩展该方法的可能性。

BACKGROUND & AIMS: Tn10, like several other transposons, exhibits a marked preference for integration into particular target sequences. Such sequences are referred to as integration hotspots and have been used to define a consensus target site in Tn10 transposition. We demonstrate that a Tn10 hotspot called HisG1, which was identified originally in vivo, also functions as an integration hotspot in vitro in a reaction where the HisG1 sequence is present on a short DNA oligomer. We use this in vitro system to define factors which are important for the capture of the HisG1 target site. We demonstrate that although divalent metal ions are not essential for HisG1 target capture, they greatly facilitate capture of a mutated HisG1 site. Analysis of catalytic transposase mutants further demonstrates that the DDE motif plays a critical role in 'divalent metal ion-dependent' target capture. Analysis of two other classes of transposase mutants, Exc+ Int- (which carry out transposon excision but not integration) and ATS (altered target specificity), demonstrates that while a particular ATS transposase binds HisG1 mutants better than wild-type transposase, Exc+ Int- mutants are defective in HisG1 capture, further defining the properties of these classes of mutants. Possible mechanisms for the above observations are considered.

背景与目标： Tn10与其他几个转座子一样，表现出对整合到特定靶序列的明显偏好。此类序列被称为整合热点，并已用于定义Tn10转座中的共有靶位点。我们证明了最初在体内鉴定的称为HisG1的Tn10热点在HisG1序列存在于短DNA寡聚物上的反应中也起着体外整合热点的作用。我们使用此体外系统来定义对于捕获HisG1靶位点很重要的因素。我们证明，尽管二价金属离子对于HisG1靶捕获不是必需的，但它们极大地促进了突变HisG1位点的捕获。催化转座酶突变体的分析进一步表明，DDE基序在 “二价金属离子依赖性” 靶捕获中起关键作用。对另外两类转座酶突变体Exc Int- (进行转座子切除但不整合) 和ATS (改变靶特异性) 的分析表明，尽管特定的ATS转座酶比野生型转座酶更好地结合HisG1突变体，但Exc Int-突变体在HisG1捕获中存在缺陷，进一步定义这些类别的突变体的属性。考虑了上述观察的可能机制。

BACKGROUND & AIMS: BACKGROUND:Accurate and automatic gene identification in eukaryotic genomic DNA is more than ever of crucial importance to efficiently exploit the large volume of assembled genome sequences available to the community. Automatic methods have always been considered less reliable than human expertise. This is illustrated in the EGASP project, where reference annotations against which all automatic methods are measured are generated by human annotators and experimentally verified. We hypothesized that replicating the accuracy of human annotators in an automatic method could be achieved by formalizing the rules and decisions that they use, in a mathematical formalism. RESULTS:We have developed Exogean, a flexible framework based on directed acyclic colored multigraphs (DACMs) that can represent biological objects (for example, mRNA, ESTs, protein alignments, exons) and relationships between them. Graphs are analyzed to process the information according to rules that replicate those used by human annotators. Simple individual starting objects given as input to Exogean are thus combined and synthesized into complex objects such as protein coding transcripts. CONCLUSION:We show here, in the context of the EGASP project, that Exogean is currently the method that best reproduces protein coding gene annotations from human experts, in terms of identifying at least one exact coding sequence per gene. We discuss current limitations of the method and several avenues for improvement.

背景与目标：

BACKGROUND & AIMS: :We have previously reported that a targeted anti-caries DNA vaccine, pGJA-P, induced accelerated and increased antibody responses compared with a non-targeted anti-caries DNA vaccine. Recently, pGJA-P/VAX, a new targeted anti-caries DNA vaccine for human trials, was constructed by replacing the pCI vector used in the construction of pGJA-P with pVAX1, the only vector authorized by the US Food and Drug Administration in clinical trials. Here, we report on our exploration of the kinetics of the antibody responses generated following pGJA-P/VAX immunization and the persistence of pGJA-P/VAX at both the inoculation site and the draining lymph nodes. Intranasal vaccination of mice with pGJA-P/VAX induced strong antibody responses that lasted for more than 6 months. Furthermore, pGJA-P/VAX could still be detected at both the inoculation site and the draining cervical lymph nodes 6 months after immunization. Thus, the persistent immune responses are likely due to the DNA depot in the host, which acts as a booster immunization.

背景与目标： : 我们以前曾报道过，与非靶向抗龋DNA疫苗相比，靶向抗龋DNA疫苗pGJA-P诱导了加速和增加的抗体反应。最近，pGJA-P/VAX是一种用于人体试验的新型靶向抗龋齿DNA疫苗，通过用pVAX1代替用于构建pGJA-P的pCI载体，这是美国食品药品监督管理局在临床试验中唯一授权的载体。在这里，我们报告了我们对pGJA-P/VAX预防接种后产生的抗体反应的动力学以及pGJA-P/VAX在接种部位和引流淋巴结的持久性的探索。用pGJA-P/VAX对小鼠进行鼻内疫苗接种可诱导持续6个月以上的强烈抗体反应。此外预防接种后6个月，在接种部位和引流颈淋巴结中仍可检测到pGJA-P/VAX。因此，持续的免疫反应可能是由于宿主中的DNA储存库而起加强预防接种作用。

BACKGROUND & AIMS: :The genomes of bacterial and viral DNA contain a much higher frequency of unmethylated CpG dinucleotides than those of vertebrates. This difference in genome structure allows the innate immune system of vertebrates to distinguish bacterial or viral DNA from self-DNA, and consequently to perceive a 'danger signal' when bacterial or viral DNA is encountered. Multiple sources of evidence suggest that CpG motifs, including bacterial DNA and CpG ODNs (synthetic oligodeoxynucleotides containing unmethylated CpG), are capable of evoking a range of immunostimulatory effects in vertebrates and have a tremendous potential to be used as therapeutic agents and adjuvants. CpG motifs with different sequences have been shown to induce various types or levels of immunostimulatory responses whereas the immunostimulatory effects of CpG motifs are species-specific. A better understanding of CpG recognition at the molecular level is fundamental to the identification of those motifs that have desired immunostimulatory responses. It is hoped that this would allow the optimization and application of CpG motifs as therapeutic agents and adjuvants, for numerous diseases in various species.

背景与目标： : 细菌和病毒DNA的基因组含有比脊椎动物更高的未甲基化CpG二核苷酸的频率。基因组结构的这种差异使脊椎动物的先天免疫系统能够将细菌或病毒DNA与自身DNA区分开，从而在遇到细菌或病毒DNA时感知到 “危险信号”。多种证据表明，CpG基序，包括细菌DNA和CpG odn (含有未甲基化CpG的合成寡脱氧核苷酸)，能够在脊椎动物中引起一系列免疫刺激作用，并具有用作治疗剂和佐剂的巨大潜力。已显示具有不同序列的CpG基序可诱导各种类型或水平的免疫刺激反应，而CpG基序的免疫刺激作用是物种特异性的。在分子水平上更好地理解CpG识别对于鉴定具有所需免疫刺激反应的基序至关重要。希望这将允许CpG基序作为治疗剂和佐剂的优化和应用，以治疗各种物种中的许多疾病。

BACKGROUND & AIMS: The denaturation-renaturation thermal hysteresis was used to investigate the kinetics of the helix-coil equilibrium of four 22-base pair homopurine-homopyrimidine duplex oligonucleotides with fractional G x C base pair content (f(G x C)) between 0.14 and 0.5. In 20 mM NaCl and 20 mM Tris-HCl at pH 7.0 and at hydrostatic pressures up to 200 MPa, a two-state bimolecular reaction mechanism adequately described the observed kinetics. At 1 MPa and 47 degrees C, the rate constant for helix formation, k1, increased by a factor of 210, and the reverse rate constant, k(-1), decreased by a factor of 420 upon increasing f(G x C) from 0.14 to 0.5. The activation energies for formation of the duplexes were negative and relatively insensitive to f(G x C). The pressure-induced change in the rate constants is related to the activation volume of the reaction step. Pressure causes k1 to become larger, and the magnitude of the change in k1 with pressure increases the lower the f(G x C) value. Thus, when f(G x C) = 0.14, the activation volume for forward reaction, delta V++(1), equals -20 mL/mol, while when f(G x C) = 0.5, delta V++(1) = -6.7 mL/mol. The rate constant for strand separation, k(-1), decreases at high pressure. The activation volume for this step, delta V++(1), varies from 17 to 1.6 mL/mol when f(G x C) = 0.14 and 0.5, respectively. The delta V for helix formation calculated from the activation parameters changed from -23 mL/mol when f(G x C) = 0.14 to -5.8 mL/mol when f(G x C) = 0.5. From extrapolation, it is estimated that the molar volume change for formation of G x C base pairs in homopurine-homopyrimidine sequences is approximately 0 mL/mol. Parameters calculated from kinetics of other two duplex molecules, when f(G x C) = 0.23 and 0.32, lie between these extremes.

背景与目标： 变性-复性热滞后用于研究0.14和0.5之间具有分数G x C碱基对含量 (f(G x C)) 的四种22碱基对高嘌呤-高嘧啶双链体寡核苷酸的螺旋-螺旋平衡动力学。在pH 7.0和高达200 MPa的静水压力下，在20 mM NaCl和20 mM Tris-HCl中，两态双分子反应机理充分描述了观察到的动力学。在1 mpa和47 ℃ 下，当f(G x C) 从0.14增加到0.5时，螺旋形成的速率常数k1增加了210倍，反向速率常数k(-1) 降低了420倍。形成双链体的活化能为负，并且对f(G x C) 相对不敏感。压力引起的速率常数变化与反应步骤的活化体积有关。压力导致k1变大，并且k1随压力变化的幅度增加，f(G x C) 值越低。因此，当f(G x C) = 0.14时，正向反应的活化体积 δ V ++(1) 等于-20 mL/mol，而当f(G x C) = 0.5时，δ V ++(1) = -6.7 mL/mol。在高压下，链分离的速率常数k(-1) 降低。当f(G x C) = 0.14和0.5时，该步骤的活化体积 Δ V ++(1) 分别从17至1.6 mL/mol变化。由活化参数计算的螺旋形成的 δ V从f (gxc) = 0.14时的-23 mL/mol变化到f (gxc) = 0.5时的-5.8 mL/mol。根据外推法，估计在均嘌呤-高嘧啶序列中形成G x C碱基对的摩尔体积变化约为0毫升/mol。当f(G x C) = 0.23和0.32时，根据其他两个双链体分子的动力学计算出的参数介于这些极端之间。

BACKGROUND & AIMS: The polymerase chain reaction has been applied to the detection of Escherichia coli DNA in the upper gut contents of Lindow Man, an Iron Age bog body dated to ca 300 BC. With sets of primers from the uidA and lacZ genes, E. coli DNA could be detected reproducibly. Initial attempts at detecting DNA from freshly voided faeces from a healthy volunteer were unsuccessful due to inhibition of the reaction. Development of a method, based on guanidine thiocyanate and silica extraction and purification of the DNA fragments, facilitated the detection of the E. coli DNA in both freshly voided faeces and the upper gut contents of Lindow Man. These findings indicate that it may be possible to study the existence of infectious diseases in ancient civilizations and to learn more about the evolution of microbes.

背景与目标： 聚合酶链反应已用于检测Lindow Man的上肠内容物中的大肠杆菌DNA，Lindow Man是铁器时代的沼泽体，可追溯至公元前300年。使用uidA和lacZ基因的引物组，可以重复检测大肠杆菌DNA。由于抑制反应，最初尝试从健康志愿者的新鲜排空粪便中检测DNA的尝试均未成功。基于硫氰酸胍和二氧化硅提取和纯化DNA片段的方法的开发，有助于检测新鲜排空的粪便和Lindow Man的上肠内容物中的大肠杆菌DNA。这些发现表明，可能有可能研究古代文明中传染病的存在，并更多地了解微生物的进化。

BACKGROUND & AIMS: :Two alternative haplotypes at the complex locus controlling hemoglobin beta chain synthesis in Mus musculus were compared at the DNA level. As expected, Hbbd homozygotes--which as adults synthesize two species of beta chain--have two genes for beta globin. Adult mice homozygous for the Hbbs haplotype make only a single type of beta polypeptide, yet they also have two beta globin genes. Apparently the two Hbbs genes encode identical proteins, or one of the two genes is not detectably expressed. The Hbbs and Hbbd haplotypes are thus more similar at the DNA level than studies of their polypeptide products have indicated.

背景与目标： : 在DNA水平上比较了控制小家鼠血红蛋白 β 链合成的复杂位点的两种替代单倍型。正如预期的那样，Hbbd纯合子-成年后合成了两个 β 链物种-具有两个 β 球蛋白基因。Hbbs单倍型纯合的成年小鼠仅产生一种 β 多肽，但它们也有两个 β 球蛋白基因。显然，这两个Hbbs基因编码相同的蛋白质，或者这两个基因中的一个无法检测到表达。因此，hbb和Hbbd单倍型在DNA水平上比其多肽产物的研究更相似。