Protein-protein interaction: a genetic selection for compensating mutations at the barnase-barstar interface.

Barnase and barstar are trivial names of the extracellular RNase and its intracellular inhibitor produced by Bacillus amyloliquefaciens. Inhibition involves the formation of a very tight one-to-one complex of the two proteins. With the crystallographic solution of the structure of the barnase-barstar complex and the development of methods for measuring the free energy of binding, the pair can be used to study protein-protein recognition in detail. In this report, we describe the isolation of suppressor mutations in barstar that compensate for the loss in interaction energy caused by a mutation in barnase. Our suppressor search is based on in vivo selection for barstar variants that are able to protect host cells against the RNAse activity of those barnase mutants not properly inhibited by wild-type barstar. This approach utilizes a plasmid system in which barnase expression is tightly controlled to keep the mutant barnase gene silent. When expression of barnase is turned on, failure to form a complex between the mutant barnase and barstar has a lethal effect on host cells unless overcome by substitution of the wild-type barstar by a functional suppressor derivative. A set of barstar suppressors has been identified for barnase mutants with substitutions in two amino acid positions (residues 102 and 59), which are critically involved in both RNase activity and barstar binding. The mutations selected as suppressors could not have been predicted on the basis of the known protein structures. The single barstar mutation with the highest information content for inhibition of barnase (H102K) has the substitution Y30W. The reduction in binding caused by the R59E mutation in barnase can be partly reversed by changing Glu-76 of barstar, which forms a salt bridge with the Arg-59 in the wild-type complex, to arginine, thus completing an interchange of the two charges.

The crystal structure of an N-terminal two-domain fragment of vascular cell adhesion molecule 1 (VCAM-1): a cyclic peptide based on the domain 1 C-D loop can inhibit VCAM-1-alpha 4 integrin interaction.

Vascular cell adhesion molecule 1 (VCAM-1) represents a structurally and functionally distinct class of immunoglobulin superfamily molecules that bind leukocyte integrins and are involved in inflammatory and immune functions. X-ray crystallography defines the three-dimensional structure of the N-terminal two-domain fragment that participates in ligand binding. Residues in domain 1 important for ligand binding reside in the C-D loop, which projects markedly from one face of the molecule near the contact between domains 1 and 2. A cyclic peptide that mimics this loop inhibits binding of alpha 4 beta 1 integrin-bearing cells to VCAM-1. These data demonstrate how crystallographic structural information can be used to design a small molecule inhibitor of biological function.

How Does the Denver Public Library System Respond to its Customer's Requests for Global Information?

The interaction between globally available information and public library users is a changing one. Global information is readily available yet provider and user struggle to find efficiencies of time and resources. As a primary resource of global information the Denver Public Library (DPL) is approaching this challenge by providing changing technology to a changing user and by providing a customized approach to immigrant populations. DPL provides global information to library users through collections, programs and Internet. Internet and collections global information usage cannot be directly measured due to privacy restrictions. Only 12.5% of general user programs focus on global information. Four percent of budget serves the immigrant users. This is greater than national averages.

Can model Hamiltonians describe the electron–electron interaction in π-conjugated systems?: PAH and graphene

Model Hamiltonians have been, and still are, a valuable tool for investigating the electronic structure of systems for which mean field theories work poorly. This review will concentrate on the application of Pariser–Parr–Pople (PPP) and Hubbard Hamiltonians to investigate some relevant properties of polycyclic aromatic hydrocarbons (PAH) and graphene. When presenting these two Hamiltonians we will resort to second quantisation which, although not the way chosen in its original proposal of the former, is much clearer. We will not attempt to be comprehensive, but rather our objective will be to try to provide the reader with information on what kinds of problems they will encounter and what tools they will need to solve them. One of the key issues concerning model Hamiltonians that will be treated in detail is the choice of model parameters. Although model Hamiltonians reduce the complexity of the original Hamiltonian, they cannot be solved in most cases exactly. So, we shall first consider the Hartree–Fock approximation, still the only tool for handling large systems, besides density functional theory (DFT) approaches. We proceed by discussing to what extent one may exactly solve model Hamiltonians and the Lanczos approach. We shall describe the configuration interaction (CI) method, a common technology in quantum chemistry but one rarely used to solve model Hamiltonians. In particular, we propose a variant of the Lanczos method, inspired by CI, that has the novelty of using as the seed of the Lanczos process a mean field (Hartree–Fock) determinant (the method will be named LCI). Two questions of interest related to model Hamiltonians will be discussed: (i) when including long-range interactions, how crucial is including in the Hamiltonian the electronic charge that compensates ion charges? (ii) Is it possible to reduce a Hamiltonian incorporating Coulomb interactions (PPP) to an 'effective' Hamiltonian including only on-site interactions (Hubbard)? The performance of CI will be checked on small molecules. The electronic structure of azulene and fused azulene will be used to illustrate several aspects of the method. As regards graphene, several questions will be considered: (i) paramagnetic versus antiferromagnetic solutions, (ii) forbidden gap versus dot size, (iii) graphene nano-ribbons, and (iv) optical properties.

The Determinants of Investment in Information and Communication Technologies. Bruges European Economic Research (BEER) Papers 16/March 2010

In this paper we investigate the determinants of ICT investment at the macro level for a panel of ten countries over the period 1992-2005. We argue that, since ICT is a General Purpose Technology, its diffusion can be understood only considering the interaction with institutional and structural factors. The empirical results are in line with this view: facilitating factors such as changes in regulation, human capital and the sectoral composition of the economy are relevant determinants for increasing ICT investment.

Granular computing as a basis of human–data interaction: a cognitive cities use case

The article proposes granular computing as a theoretical, formal and methodological basis for the newly emerging research field of human–data interaction (HDI). We argue that the ability to represent and reason with information granules is a prerequisite for data legibility. As such, it allows for extending the research agenda of HDI to encompass the topic of collective intelligence amplification, which is seen as an opportunity of today’s increasingly pervasive computing environments. As an example of collective intelligence amplification in HDI, we introduce a collaborative urban planning use case in a cognitive city environment and show how an iterative process of user input and human-oriented automated data processing can support collective decision making. As a basis for automated human-oriented data processing, we use the spatial granular calculus of granular geometry.

Light sheet fluorescence microscopy for in situ cell interaction analysis in mouse lymph nodes.

Reactive lymph nodes (LNs) are sites where pMHC-loaded dendritic cells (DCs) interact with rare cognate T cells, leading to their clonal expansion. While DC interactions with T cell subsets critically shape the ensuing immune response, surprisingly little is known on their spatial orchestration at physiologically T cell low precursor frequencies. Light sheet fluorescence microscopy and one of its implementations, selective plane illumination microscopy (SPIM), is a powerful method to obtain precise spatial information of entire organs of 0.5-10mm diameter, the size range of murine LNs. Yet, its usefulness for immunological research has thus far not been comprehensively explored. Here, we have tested and defined protocols that preserve fluorescent protein function during lymphoid tissue clearing required for SPIM. Reconstructions of SPIM-generated 3D data sets revealed that calibrated numbers of adoptively transferred T cells and DCs are successfully detected at a single cell level within optically cleared murine LNs. Finally, we define parameters to quantify specific interactions between antigen-specific T cells and pMHC-bearing DCs in murine LNs. In sum, our studies describe the successful application of light sheet fluorescence microscopy to immunologically relevant tissues.

An investigation of the effectiveness of existing bridge design methodology in providing adequate structural resistance to seismic disturbances : Phase III, Nonlinear soil-structure interaction of skew highway bridges : final report : prepared for Federal Highway Administration, Offices of Research and Development /

Bibliography: p. 46-48.

Annotated bibliography on wave-current interaction /

This annotated bibliography discusses 60 key publications dealing with wave-current interaction. Each entry includes a bibliographic identification, keywords, a discussion of contents, and a statement of coastal engineering significance. An index of the entries by keywords is provided in an appendix. The recent growth of the wave-current interaction field is indicated by the fact that more than 30 percent of the selected publications were published in 1978 and 1979. (Author).

Pipe interaction with the backfill envelope.

"June 1999."

Family style and environmental interaction /

Mode of access: Internet.

Structural interaction with control systems.

Cover title.

A testbed for providing uniformity to user-computer interaction languages /

"Issued August 1980."

Analysis of ground-liner interaction for tunnels /

Mode of access: Internet.

Interaction of wood species in different types of forests. (Vzaimodeistvie drevesnykh porod v razlichnykh tipakh lesa). Translated from Russian.

"TT 70-57224."