Conservation and Divergence Between P22-like Bacteriophages Coat Protein’s I-domains and Procapsid-like Particles

Conservation and Divergence Between P22-like Bacteriophages Coat Protein’s I-domains and Procapsid-like Particles Therese N. Tripler, PhD University of Connecticut, 2019 P22, CUS-3 and Sf6 are distantly related bacteriophages that belong to the P22-like group based on capsid protein sequence similarity. Despite being distantly related they share important similarities. They form T=7 icosahedral capsids to protect their dsDNA, have capsid proteins that adopt the HK97 fold with an inserted domain, share similar arrangement of their structural genes in their genomes, and infect human enteric pathogens. P22, CUS-3and Sf6 infect Salmonella enterica, Escherichia coli, and Shigella flexneri, respectively. Here, we explored structural differences between the inserted domains (I-domains), differences in CUS-3 and Sf6 bacteriophage procapsid-like particle assembly and stability, and the effects of Sf6 scaffolding protein truncations on assembly. The P22, CUS-3 and Sf6 I-domains adopt a six-stranded anti-parallel b-barrel with important differences. Differences are found between loop regions, electrostatic surfaces that are found at the interface between the I-domain and the protein core, and surface TUT (threonine-hydrophobic-threonine) motifs possibly important for carbohydrate interactions. Thus, the insertion domains may have evolved to fit different functional needs in capsid stability, assembly, and coat protein folding. Like P22, CUS-3 and Sf6 coat and scaffolding proteins are shown here to assemble into procapsid-like particles in the absence of all other structural proteins. CUS-3 and Sf6 procapsid-like particles were found to be less stable compared with P22. This provides evidence that these assembly systems are governed by differences in their electrostatic and hydrophobic interactions. For P22 bacteriophage, scaffolding protein nucleates and directs capsid assembly. In P22 assembly, the C-terminal is necessary to form procapsids. Sf6 truncated scaffolding protein containing residues 1-155 formed mostly T=7 procapsid-like particles similar to those particles formed by full-length scaffolding protein. Unlike P22, the C-terminal of scaffolding protein is not necessary for assembly

1861-10-30 Surgeon Charles S. Tripler, Medical Director of the Army of the Potomac, requests commissioning of a surgeon for the 3rd Regiment

https://digitalmaine.com/cw_me_3rd_regiment_corr/1157/thumbnail.jp

Spatio-temporal development of forests - Current trends in field methods and models

We present a critical review of current trends in research of spatio-temporal development of forests. The paper addresses (1) field methods for the development of spatially-explicit models of forest dynamics and their integration in models of forest dynamics, (2) strengths and limitations of traditional patch models versus spatially-explicit, individual-based models, and (3) the potential for moment-based methods in the analysis of forest dynamics. These topics are discussed with reference to their potential for solving open questions in the studies of forest dynamics. The study of spatio-temporal processes provides a link between pattern and process in plant communities, and plays a crucial role in understanding ecosystem dynamics. In the last decade, the development of spatially-explicit, individual-based models shifted the focus of forest dynamics modelling from the dynamics of discrete patches to the interactions among individual organisms, thus encapsulating the theory of "neighbourhood" dynamics. In turn, the stochastic properties and the complexity of spatially-explicit, individual-based models gave rise to the development of a new suite of so-called moment-based models. These new models describe the dynamics of individuals and of pairs of individuals in terms of their densities, thus directly capturing second-order information on spatial structure. So far, this approach has not been applied to forests; we indicate extensions needed for such applications. Moment-based models may be an important complement to spatially explicit individual-based models in developing a general spatial theory of forest dynamics. However, both kinds of models currently focus on fine scales, whereas a critical issue in forest dynamics is to understand the interaction of fine-scale processes with coarser-scale disturbances. To obtain a more complete picture of forest dynamics, the relevant links and interactions between fine-, intermediate-, and coarse-scale processes ought to be identified. Intensive links between modelling work and field studies designed across different scales are a promising means to create a new perspective on forest dynamics

Potassium : a neglected nutrient in global change

L'article inclou sis apèndixsAim: Potassium (K) is the second most abundant nutrient after nitrogen (N) in plant photosynthetic tissues. Thousands of physiological and metabolic studies in recent decades have established the fundamental role of K in plant function, especially in water use efficiency and economy, and yet macroecological studies have mostly overlooked this nutrient.- Methods: We have reviewed available studies on the contents, stoichiometries and roles of potassium in the soil-plant system and in terrestrial ecosystems. We have also reviewed the impacts of global change drivers on K contents, stoichiometries, and roles. - Conclusions: The current literature indicates that K, at a global level, is as limiting as N and phosphorus (P) for plant productivity in terrestrial ecosystems. K limitation has been seen up to some degree in 70% of all studied terrestrial ecosystems. However, atmospheric K deposition from human activities represents higher amounts than that from natural sources in some areas. We are far from understanding the K fluxes between the atmosphere and land, and the role of anthropogenic activities in these fluxes. The increasing aridity expected in wide areas of the world makes K more critical through its role in water use efficiency. N deposition exerts a strong impact on the ecosystem K-cycle, decreasing K availability and increasing K limitation. Plant invasive success is enhanced by higher soil K availability, especially in environments without strong abiotic stresses. The impacts of other global change drivers, such as increasing atmospheric CO² or changes in land use remain to be elucidated. Current models of the responses of ecosystems and carbon storage to projected global climatic and atmospheric changes are now starting to consider N and P, but they should also consider K, mostly in arid and semiarid ecosystems

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Personal Papers (MS 80-0002)

Invoice for items sold to Mr. Daniel W. Kempner by F. R. Tripler & Co., including two belts and tax worth $10.20

1861-10-30 Surgeon Charles S. Tripler, Medical Director of the Army of the Potomac, requests commissioning of a surgeon for the 3rd Regiment

https://digitalmaine.com/cw_me_3rd_regiment_corr/1157/thumbnail.jp