Surface-induced dissociation shows potential to be more informative than collision-induced dissociation for structural studies of large systems

The ability to preserve noncovalent, macromolecular assemblies intact in the gas phase has paved the way for mass spectrometry to characterize ions of increasing size and become a powerful tool in the field of structural biology. Tandem mass spectrometry experiments have the potential to expand the capabilities of this technique through the gas-phase dissociation of macromolecular complexes, but collisions with small gas atoms currently provide very limited fragmentation. One alternative for dissociating large ions is to collide them into a surface, a more massive target. Here, we demonstrate the ability and benefit of fragmenting large protein complexes and inorganic salt clusters by surface-induced dissociation (SID), which provides more extensive fragmentation of these systems and shows promise as an activation method for ions of increasing size.     

Solid-phase and microwave-assisted syntheses of 2,5-diketopiperazines: small molecules with great potential

Diketopiperazines (DKPs) are a well-known class of heterocycles that have recently emerged as a promising biologically active scaffold. Solid-phase organic synthesis has become an important tool in the combinatorial exploration of these privileged structures, expediting the synthesis and, therefore, the discovery of active compounds. To date, certain DKPs have shown potent activities against a range of diseases and biological phenomena, including bacterial infections, various cancers, asthma, infertility, premature labor, and HIV. Recent applications of solid-phase DKP synthesis, with a particular focus on cyclative cleavage and microwave-assisted reactions, are highlighted herein.     

Information sharing impact of stochastic diffusion search on differential evolution algorithm

This work details the research aimed at applying the powerful resource allocation mechanism deployed in stochastic diffusion search (SDS) to the differential evolution (DE), effectively merging a nature inspired swarm intelligence algorithm with a biologically inspired evolutionary algorithm. The results reported herein suggest that the hybrid algorithm, exploiting information sharing between the population elements, has the potential to improve the optimisation capability of classical DE algorithms. This claim is verified by running several experiments using state-of-the-art benchmarks. Additionally, the significance of the frequency within which SDS introduces communication and information exchange is also investigated.     

About the structure of cellulose: debating the Lindman hypothesis

The hypothesis advanced in this issue of CELLULOSE [Springer] by Bjorn Lindman, which asserts that the solubility or insolubility characteristics of cellulose are significantly based upon amphiphilic and hydrophobic molecular interactions, is debated by cellulose scientists with a wide range of experiences representing a variety of scientific disciplines. The hypothesis is based on the consideration of some fundamental polymer physicochemical principles and some widely recognized inconsistencies in behavior. The assertion that little-recognized (or under-estimated) hydrophobic interactions have been the reason for a tardy development of cellulose solvents provides the platform for a debate in the hope that new scientific endeavors are stimulated on this important topic.     

Copper catalyzed oxidation of organozinc halides

A wide range of organozinc substrates may be oxidized in the presence of catalytic copper to give carbon-carbon bonds in high yield.     

Interception of quorum sensing in Staphylococcus aureus: a new niche for peptidomimetics

Pathogenesis in Staphylococcus aureus is dependent on local cell density and is regulated in part by small macrocyclic peptides. Natural and artificial peptide inhibitors of this quorum sensing response have been synthesized and evaluated in structure-activity relationship studies. These investigations have illuminated the quorum sensing mechanism and set the stage for the design of biostable, peptidomimetic inhibitors that could be developed ultimately as therapeutics.     

Sounds from an oil production island in the Beaufort Sea in summer: characteristics and contribution of vessels

The objective of this study was to determine the levels, characteristics, and range dependence of underwater and in-air sounds produced during the open-water seasons of 2000-2003 by the Northstar oil development, located in nearshore waters of the Alaskan Beaufort Sea. Specifically, sounds originating at the island itself (from construction, drilling, and oil production activities) were compared with sounds produced by vessels performing island support. Sounds were obtained with boat-based recordings (at distances up to 37 km from Northstar), a cabled hydrophone (distance approximately 450 m), and with autonomous seafloor recorders (distance approximately 22 km). Vessels (crew boat, tugs, self-propelled barges) were the main contributors to the underwater sound field and were often detectable underwater as much as approximately 30 km offshore. Without vessels, broadband island sounds reached background values at 2-4 km. Island sound levels showed more variation (lower min, higher max) during construction than during drilling and production. In-air broadband measurements were not affected by the presence of vessels and reached background values 1-4 km from Northstar. However, one airborne tone (81 Hz) believed to originate at Northstar was still detectable in the spectrum 37 km away.     

Hard-segment domain sizes in MDI/diol polyurethane elastomers

Wide-angle x-ray line broadening methods have been used to determine the crystallite size and degree of distortion for the crystalline hard domains in MDI/diol polyurethane elastomers. Crystallite widths have been determined from the integral breadths of the 00l reflections following correction for distortions of the second kind according to the method Hosemann for polymers prepared using ethylene glycol, propandiol, butandiol, and hexandiol as the chain extender. These data relate to the width of the crystallites along the chain axis and thus can be interpreted in terms of the morphology of the hard domains. The crystallite sizes increase and the distortions decrease with increasing elongation and annealing time, and the sizes tend toward asymptotic values which correspond approximately to the average lengths of the hard-segment chains. These results rule out any appreciable folding of the hard-segment chains and point to a model for the hard domains formed by lateral aggregation of extended hard segments.     

Effect of changing reagent energy. IX. Dependence of reaction rate on rotational excitation in HX(J:ν) + Na → H + NaX (X = F, Cl)

The chemiluminescence depletion (CD) method has been used to measure relative rate constants k(J), i.e. rate of reaction as a function of the r     

On generating state space equations of a linear constant coefficient system

The details of the linear algebra which must be performed in order to generate state space equations from primitive equations of the linear constant coefficient ordinary differential mathematical model are presented. The applicability of the procedure is not dependent on any modeling philosophy and/or regimen. In addition to generating the state variable representation of the system, the procedure also generates equations which relate all other system internal variables to the system states and the system input variables. The treatment is complete and identifies all the operations which must be done in implementing a digital computer automation of the process. Some useful insights into the effects of ill-posed mathematical models and of modeling errors result from the treatment.The author is indebted to several reviewers and colleagues for valuable suggestions for improvement and for encouragement.