Stability constants of metal complexes of phosphonoacetic acid

The antiviral drug, phosphonoacetic acid (PAA), forms stable complexes with Mg²⁺, Ca²⁺, Cu²⁺ and Zn²⁺. Stability constants of these complexes were determined in aqueous solution (0.15 M in KNO₃, 37°) by potentiometric titration. Mixed ligand complex formation of Cu²⁺ and Zn²⁺ with PAA and glycinate ion, and with PAA and histidinate ion, was studied. In a theoretical model for blood plasma, PAA affects the distribution of Mg²⁺ and, to a lesser extent, Ca²⁺.     

The discovery of the nature of ferredoxin in photosystems: A recollection

I describe here my recollection of the story of the discovery of the nature of ferredoxin in photosystems that began in 1965: this story involved the EPR measurements by a young physicist J.H.M. Thornley, using samples provided by J.F. Gibson and D. Hall, and in collaboration with F.R. Whatley.     

Filmed Dreams: Cinematographic and Story Line Characteristics of the Cinematic Dreamscapes of John Sayles

The authors characterize the filmed dreamscapes of John Sayles though a structured interview with the screenwriter/director and an analysis of cinematographic and story line techniques utilized in creating dreamscapes in two of his films. The filmmaker uses complex techniques to produce believable dreams in otherwise naturalistic films by isolating the dream sequence and altering sound, color, cinematography, story, time, visual perspective and physical properties of the perceived external reality of the dream. This perceptual and orienting framework required to produce a believable dream on film may reflect innate characteristics of the dream state.     

Morphogenesis, Dictyostelium, and the search for shared developmental processes

In the 1930s John Tyler Bonner began studying the slime mold, Dictyostelium discoideum, as a way to investigate how organisms develop. With a life cycle that includes periods of unicellularity and multicellularity, Dictyostelium raises questions fundamental to development and evolution. In Morphogenesis: An Essay on Development (1952), Bonner built on his work with Dictyostelium to inform developmental theory and practice. By exploring how Bonner’s early work with Dictyostelium motivated his synthetic approach in Morphogenesis, this paper presents an example of how those who studied development sought ways to gain traction in the rapidly changing life sciences. While a biochemical viewpoint of development became dominant, morphogenesis provided a way to reintroduce and emphasize biological organization at the organismal level. Bonner’s early work offers a window to mid-twentieth century studies of development, an understudied area in the history of science, and shows that it was a time when growing experimental evidence enabled new ways of thinking about the relationship between ontogeny and evolution, and more broadly, about how the parts of nature might fit together.     

A case study in explanatory power: John Snow's conclusions about the pathology and transmission of cholera

In the mid-1800s, there was much debate about the origin or ‘exciting cause’ of cholera. Despite much confusion surrounding the disease, the so-called miasma theory emerged as the prevalent account about cholera’s cause. Going against this mainstream view, the British physician John Snow inferred several things about cholera’s origin and pathology that no one else inferred. Without observing the vibrio cholerae, however,—data unavailable to Snow and his colleagues—, there was no way of settling the question of what exactly was causing cholera and how, or if, it was passed on. The question then arises as to how Snow arrived at conclusions so systematically different from those of his opponents. In this paper, I want to look at Snow’s reasoning in some detail, and show that there were certain principles, explanatory power in particular, that were epistemologically important to Snow in their own right. I will show that Snow himself takes explanatory power to be an epistemic property, and makes explicit links between explanatory power and confirmation. Systematically juxtaposing Snow’s claims and his opponents’, I will show that Snow was right to tout the explanatory power of his theory, and that his conclusions about the epistemic superiority of his theory over that of the miasmatists’ were justified.     

Nematode communities inhabiting the soft deep-sea sediment in polymetallic nodule fields: do they differ from those in the nodule-free abyssal areas?

This study addresses whether or not nematode assemblages inhabiting the soft sediment in abyssal nodule fields are unique and differ from those occurring in the nodule-free abyssal areas. This question is important for the evaluation of possible diversity losses caused by nodule mining operations. The analysis involved seven datasets at genus-level of nematode assemblages from three nodule-bearing abyssal areas in the Pacific (the Clarion-Clipperton Fracture Zone or CCFZ, and the Peru Basin) and the Indian Ocean (CIOB), and five datasets from nodule-free abyssal regions (the Atlantic Ocean). Only individuals identified to valid genera were used in the analysis. Overall, more than 20,000 nematode individuals from 90 samples were analysed. The analyses showed that the nematode communities in the nodule fields did differ from those in the nodule-free abyss. The nodule fields are characterized by a higher microhabitat heterogeneity, which resulted in a higher diversity of nematode communities inhabiting the nodule fields. However, one set of dominant taxa (Monhysteridae, Microlaimus, Acantholaimus, Theristus and Desmoscolex) was identical for both the nodule-bearing and nodule-free abyss, although some genera were strongly and significantly associated with either the nodule-free abyss (Microlaimus) or the nodule-bearing abyssal regions (Capsula). On the other hand, nematode assemblages at nodule-bearing and nodule-free sites within the nodule-bearing abyss proved to be similar at the genus level. This makes it possible for the nodule-free sites to serve as donors of colonizers for the mining-impacted nodule-bearing abyss. However, this suggestion has to be treated with caution, because the species-level differences have not been tested yet.     

NaCl胁迫对滨梅扦插苗生物量和水分积累的影响

以1年生滨梅(Prunus maritima Marshall)扦插苗为实验材料,在盆栽条件下用质量浓度为0.15%、0.29%、0.58%、0.88%、1.17%、1.46%的NaCl溶液进行盐胁迫处理,测定胁迫后根、茎、叶Na+、K+含量以及全叶、一年生茎、二年生茎和根系生物量、含水率、根系活力变化,探讨滨梅的抗盐胁迫机制。结果显示:(1)盐胁迫80d后,随着盐胁迫强度提高,滨梅植株根、茎、叶Na+含量显著提高,而其根、茎K+含量显著降低,根、茎、叶K+/Na+值显著降低;根Na+含量在低于0.58%NaCl胁迫下显著高于茎、叶,而在高于0.58%NaCl胁迫下却表现为叶Na+含量显著高于根、茎。(2)滨梅根、茎、叶生物量均随盐胁迫强度的提高呈先增加后减少的趋势;随着盐胁迫时间的延长,茎、叶生物量在低于0.58%NaCl胁迫下均呈积累趋势,且茎生物量在0.58%NaCl胁迫下显著提高,而根、一年生茎、叶生物量在高于0.58%NaCl胁迫下均显著下降。(3)滨梅茎、叶含水率均随盐胁迫强度的增加呈先增加后减少的趋势,而随着胁迫时间的延长呈逐渐减少趋势;根系活力及根含水率均随盐胁迫强度的提高而增加,但根含水率随着胁迫时间的延长变化不明显。由此可见,滨梅能通过根系稀释并蓄积Na+,保护地上部分正常生长,当进入根系的Na+量超过吸收阈值时,Na+迅速在叶中积累储存,且叶中较高含量的K+对Na+形成了有效的缓冲。     

Activation of Rubisco controls CO<Subscript>2</Subscript> assimilation in light: a perspective on its discovery

CO₂ fixation during photosynthesis is regulated by the activity of ribulose bisphosphate carboxylase (Rubisco). This conclusion became more apparent to me after CO₂-fixation experiments using isolated spinach chloroplasts and protoplasts, purified Rubisco enzyme, and intact leaves. Ribulose bisphosphate (RuBP) pools and activation of Rubisco were measured and compared to ¹⁴CO₂ fixation in light. The rates of ¹⁴CO ₂ assimilation best followed the changes in Rubisco activation under moderate to high light intensities. RuBP pool sizes regulated ¹⁴ ₂ assimilation only in very high CO₂ levels, low light and in darkness. Activation of Rubisco involves two separate processes: carbamylation of the protein and removal of inhibitors blocking carbamylation or blocking RuBP binding to carbamylated sites before reaction with CO₂ or O₂. This revised version was published online in June 2006 with corrections to the Cover Date.     

From structure to solutions: the role of basic research in developing anthrax countermeasures: Microbiology Graduate Program Seminar: Anthrax toxin

Dr. John Collier traced the discoveries that elucidated the structure and function of the anthrax toxin in his talk "Anthrax Toxin," which was part of the Microbiology Graduate Program Seminar Series at Yale School of Medicine on February 23, 2012. Dr. Collier, Professor of Microbiology and Immunobiology at Harvard University, began by noting the advantages to studying anthrax pathogenesis in a biosafety level-1 lab. This designation does not merely facilitate his research, but also reflects a larger trend of basic research being leveraged to develop translational applications. Basic research on toxin structure has led to the development of a vaccine by Dr. Collier's group. Next-generation prophylactics also may stem from recent discoveries uncovering a role for cellular cofactors that mediate toxin function. Finally, basic research into the toxin substructure has facilitated efforts to change the receptor tropism to target dysregulated cells for therapeutic purposes. The urgency around biodefense agents makes the choice of research priorities a salient issue. As such, this author submits that basic research occupies a unique and lucrative niche driving clinical applications.