University of California, Santa Barbara

About: University of California, Santa Barbara is a education organization based out in Santa Barbara, California, United States. It is known for research contribution in the topics: Population & Galaxy. The organization has 30281 authors who have published 80852 publications receiving 4626827 citations. The organization is also known as: UC Santa Barbara & UCSB.

C-end rule peptides mediate neuropilin-1-dependent cell, vascular, and tissue penetration

Abstract: Screening of phage libraries expressing random peptides for binding to prostate cancer cells primarily yielded peptides that had a C-terminal arginine (or rarely lysine) residue, usually in a consensus context R/KXXR/K. Phage expressing these sequences and synthetic nanoparticles coated with them bound to and were internalized into cells. The C-terminal arginine (or lysine) was essential to the activity; adding another amino acid, or even blocking the free carboxyl group of this arginine residue by amidation, eliminated the binding and internalizing activity. An internal R/KXXR/K can be exposed and switched on by a cleavage by a protease. The strict requirement for C-terminal exposure of the motif prompted us to term the phenomenon the C-end rule (CendR). Affinity chromatography showed that the CendR peptides bind to neuropilin-1 (NRP-1) on the target cells. NRP-1 is a cell-surface receptor that plays an essential role in angiogenesis, regulation of vascular permeability, and the development of the nervous system. VEGF-A165 and other ligands of NRP-1 possess a C-terminal CendR sequence that interacts with the b1 domain of NRP-1 and causes cellular internalization and vascular leakage. Our CendR peptides have similar effects, particularly when made multivalent through coupling to a particle. We also noted a unique and important activity of these peptides: penetration and transportation through tissues. The peptides were able to take payloads up to the nanoparticle size scale deep into extravascular tissue. Our observations have implications in drug delivery and penetration of tissue barriers and tumors.

Complexity and robustness

Abstract: Highly optimized tolerance (HOT) was recently introduced as a conceptual framework to study fundamental aspects of complexity. HOT is motivated primarily by systems from biology and engineering and emphasizes, (i) highly structured, nongeneric, self-dissimilar internal configurations, and (ii) robust yet fragile external behavior. HOT claims these are the most important features of complexity and not accidents of evolution or artifices of engineering design but are inevitably intertwined and mutually reinforcing. In the spirit of this collection, our paper contrasts HOT with alternative perspectives on complexity, drawing on real-world examples and also model systems, particularly those from self-organized criticality.

A structural theory of social influence

Abstract: List of tables and figures Preface Part A. Theory and Setting: 1. Social structure and social Control 2. Toward a structural social psychology 3. A setting in the scientific community Part B. Measures of the Theoretical Constructs: 4. A structural parameterization 5. Interpersonal influence 6. Self and other 7. Social positions Part C. Analysis: 8. The structure of social space 9. The production of consensus 10. Influence of actors and social positions 11. Durkheim's vision References Index.

An analysis of the optimum node density for ad hoc mobile networks

Abstract: An ad hoc mobile network is a collection of nodes, each of which communicates over wireless channels and is capable of movement. Wireless nodes have the unique capability of transmission at different power levels. As the transmission power is varied, a tradeoff exists between the number of hops from source to destination and the overall bandwidth available to individual nodes. Because both battery life and channel bandwidth are limited resources in mobile networks, it is important to ascertain the effects different transmission powers have on the overall performance of the network. This paper explores the nature of this transmission power tradeoff in mobile networks to determine the optimum node density for delivering the maximum number of data packets. It is shown that there does not exist a global optimum density, but rather that, to achieve this maximum, the node density should increase as the rate of node movement increases.