A general strategy for epitope mapping by direct MALDI-TOF mass spectrometry using secondary antibodies and cross-linking

The combination of limited proteolysis and MALDI-TOF mass spectrometry has become an important tool for the determination of epitopes but works best with highly purified antibodies. Here we report the use of capture antibodies to reduce the need for purification of the antibody in the mass spectrometric determination of the epitope. In this new method, a secondary Fc-specific antibody, covalently bound to Sepharose beads, is used to capture the primary antibody (the antibody of interest). After capture, the two antibodies are cross-linked. The antigen is then bound to the immobilized antibodies and subjected to proteolysis using several successive proteinases. In this study, this strategy is demonstrated with a crude mouse anti-ACTH IgG solution and adrenocorticotropin (ACTH). Comparing this strategy with previous methods where the antibody is bound directly to activated beads, the new method (1) results in a higher binding capacity of the bound antibody to ACTH, (2) does not require purification of the antibody of interest, and (3) dramatically reduces the chemical background in the MALDI mass spectra.     

The beta subunit sliding DNA clamp is responsible for unassisted mutagenic translesion replication by DNA polymerase III holoenzyme

The replication of damaged nucleotides that have escaped DNA repair leads to the formation of mutations caused by misincorporation opposite the lesion. In Escherichia coli, this process is under tight regulation of the SOS stress response and is carried out by DNA polymerase III in a process that involves also the RecA, UmuD' and UmuC proteins. We have shown that DNA polymerase III holoenzyme is able to replicate, unassisted, through a synthetic abasic site in a gapped duplex plasmid. Here, we show that DNA polymerase III*, a subassembly of DNA polymerase III holoenzyme lacking the beta subunit, is blocked very effectively by the synthetic abasic site in the same DNA substrate. Addition of the beta subunit caused a dramatic increase of at least 28-fold in the ability of the polymerase to perform translesion replication, reaching 52% bypass in 5 min. When the ssDNA region in the gapped plasmid was extended from 22 nucleotides to 350 nucleotides, translesion replication still depended on the beta subunit, but it was reduced by 80%. DNA sequence analysis of translesion replication products revealed mostly -1 frameshifts. This mutation type is changed to base substitution by the addition of UmuD', UmuC, and RecA, as demonstrated in a reconstituted SOS translesion replication reaction. These results indicate that the beta subunit sliding DNA clamp is the major determinant in the ability of DNA polymerase III holoenzyme to perform unassisted translesion replication and that this unassisted bypass produces primarily frameshifts.     

Novel,Printable Energetic Polymers

Novel, simple‐to‐make energetic mono‐ and bisvinylimidazolium perchlorate monomers are prepared and characterized. These energetic monomers offer the possibility to 3D print energetic polymers that may allow decreasing the content of the energetic filler in energetic devices without compromising their energetic properties. The new printable materials are suited for photocuring‐based additive manufacturing (AM), techniques, offering not only a large degree of control over the mechanical and energetic properties of the resulting solids, but also the production of complex geometries at high resolution.     

Visible‐light‐induced controlled/living radical polymerization of styrene with a phenyl seleno group at one terminal chain end: 1‐(Phenylseleno)ethyl benzene as a photoiniferter

The photopolymerization of styrene with a well‐defined molecular architecture and a low polydispersity index and with methyl and phenylseleno (? SePh) groups at α‐ and ω‐chain ends, respectively, was performed via a controlled/living radical polymerization with a new initiating system, 1‐(phenylseleno)ethyl benzene/tert‐butyl diphenyl (phenylseleno) silane, through the absorption of visible light at room temperature. A novel initiating living radical polymerization was examined. The yield and number‐average molecular weight (M_n) of the resulting polymer increased with the reaction time. Furthermore, a linear relationship was found in a plot of M_n versus the polymer yield. These results indicated that this polymerization proceeded through a living radical mechanism. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 348–355, 2004     

The effect of daily-activity patterns on crash involvement

The main purpose of this study is to analyze the effect of daily-activity and travel patterns on the risk of crash involvement. To this end, we develop a model that integrates daily-activity and travel choices in a single framework, recognizing that these variables affect the risk of crashes. This model can therefore provide predictions of the expected changes in risk levels from the implementation of measures that affect the daily-activity patterns and the socio-economic characteristics of the population.The empirical analysis makes use of data collected during a household survey that includes crash information and trip diaries. The model is applied in a case study of an Arab town in Israel to analyze various transportation policies. The results of this research show that in addition to individuals’ demographic and socio-economic characteristics, their daily-activity and travel patterns also have an impact on the risk of being involved in car crashes. The case study showed the potential of this framework for analyzing the effect of various social and transportation policies on road safety. To the best of our knowledge, this is the first time such relationships have been tested by using a disaggregate model and the first time activity-based models have been used to analyze exposure to the risk of road crashes.     

A Path-Based Algorithm for the Cross-Nested Logit Stochastic User Equilibrium Traffic Assignment

Abstract:   This article investigates the single-class static stochastic user equilibrium (SUE) problem with separable and additive link costs. A SUE assignment based on the Cross-Nested Logit (CNL) route choice model is presented. The CNL model can better represent route choice behavior compared to the Multinomial Logit (MNL) model, while keeping a closed form equation. The article uses a specific optimization formulation developed for the CNL model, and develops a path-based algorithm for the solution of the CNL-SUE problem based on adaptation of the disaggregate simplicial decomposition (DSD) method. The article illustrates the algorithmic implementation on a real size network and discusses the trade-offs between MNL-SUE and CNL-SUE assignment .     

Adherence in childhood diabetes: Results of a confirmatory factor analysis.

Tested the equality of the factor pattern of adherence to treatment of childhood diabetes identified by S. B. Johnson et al (see record 1988-05437-001) across 2 independent samples. Samples of 162 and 157 diabetics (aged 6–18 yrs) were studied. Factors 1–4, Exercise, Injection, Diet Type, and Eating/Testing Frequency, were confirmed. Factor 5, Diet Amount, proved to be too complex; the adherence measures comprising this factor (total calories and concentrated sweets consumed) are best treated as separate, single-indicator constructs. Results support a multivariate concept of adherence, offer insight into the nature of the components underlying diabetes adherence, and provide measurement information for reliable component estimation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Effect of Heat Treatment on the Mechanical Behavior of Commercially Pure Titanium and Zirconium Under Quasi-static and Dynamic Loading

The mechanical properties (stress–strain behavior) of three hexagonal metals, two grades of commercially pure titanium (CP-Ti) and zirconium (CP-Zr), are systematically characterized before and after heat treatment. Those materials are investigated under quasi-static (< 1 s⁻¹) and dynamic (> 2000 s⁻¹) tension, compression, dominant, and pure shear to draw general conclusions as to the effect of the same heat treatment and, specifically, dynamic shear failure propensity in those hexagonal materials. The results do not reveal any consistent influence of the texture on the overall quasi-static and dynamic mechanical (stress–strain) response of the investigated materials. However, when the propensity to dynamic shear failure is specifically considered, it appears that texture variations of the CP-Ti grades have more influence than purely microstructural changes resulting from the heat treatment for both materials. When no other changes than grain growth are induced, such as in the case of CP-Zr, it appears that grain growth does not significantly affect the dynamic shear failure toughness of this material. It therefore seems like no general conclusions can be drawn as to the effect of heat treatment and associated texture changes of these three hexagonal metals on their mechanical and failure properties. Thus, despite their common crystallographic features, those materials must be considered individually rather than as belonging to the general family of hexagonal metals.