Alternatively linking fullerene and conjugated polymers

The stereo‐electronic control over bisadditions of conjugated polymers to fullerene (C₆₀) is explored in the formation of alternating copolymers. The chemistry, resulting configuration, and properties of poly(3‐hexylthiophene)‐alt‐C₆₀ copolymers prepared by either classic pyrrolidine ring formation or an atom transfer radical addition are compared. Both routes result in controlled additions of polymers to C₆₀. Extensive macromolecular modeling through PM6 methods indicate that there is no conjugation between P3HT and C₆₀ in the systems studied. This along with 2D‐NMR, AFM, and photovoltaic characterizations of the materials indicate the importance of the structure of the modified C₆₀ and the nature of the linking group between C₆₀ and P3HT segments in determining the morphology of the copolymers in the solid state. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2304–2317, 2009     

Comparison of inert supports in laser desorption/ionization mass spectrometry of peptides: pencil lead,porous silica gel,DIOS‐chip and NALDI™ target

In the search for alternative inert surfaces replacing silicon chips in Desorption/Ionization On porous Silicon (DIOS)‐like mass spectrometry analyses, nanostructured silicon‐based NALDI? chips were evaluated in Laser Desorption/Ionization (LDI) of peptides. Comparisons were made using commercially available DIOS chips (MassPREP?‐DIOS‐target?), amorphous carbon powder from lead pencil and porous silica gel used for chromatographic purposes as reference supports. A set of synthetic model peptides presenting variable amino acid sequences of various lengths was analyzed under all conditions. The LDI responses of the four ‘matrix‐free’ techniques were compared, especially in terms of peptide detection sensitivity and overall experiment robustness. Copyright © 2009 John Wiley & Sons, Ltd.     

Arithmetical and geometrical means of generalized logarithmic and exponential functions: Generalized sum and product operators

One-parameter generalizations of the logarithmic and exponential functions have been obtained as well as algebraic operators to retrieve extensivity. Analytical expressions for the successive applications of the sum or product operators on several values of a variable are obtained here. Applications of the above formalism are considered.     

Empirical model selection in generalized linear mixed effects models

This paper focuses on model selection in generalized linear mixed models using an information criterion approach. In these models in general, the response marginal distribution cannot be analytically derived. Thus, for parameter estimation, two approximations are revisited both leading to iterative model linearizations. We propose simple model selection criteria adapted from information criteria and based on the linearized model obtained at convergence of the algorithm. The quality of derived criteria are evaluated through simulations.     

Analysis of Glycosylated Type II Interleukin-1 Receptor (IL-1R) by Imaged Capillary Isoelectric Focusing (i-cIEF)

Glycoproteins typically produce a complex charge profile due to their heterogeneous glycosylation pattern. We developed a reproducible imaged capillary isoelectric focusing (i-cIEF) method to monitor the charge variants of recombinant human Type II Interleukin-1 receptor (IL-1R), a heavily glycosylated protein expressed as a soluble receptor in Chinese Hamster Ovary (CHO) cells. This method was proved to be informative in multiple settings: monitoring of upstream process and downstream purification, analysis of in-process samples, characterization of the bulk drug substance, as well as testing of stability samples during drug development. The i-cIEF method was efficient at detecting changes in the charge isoform profile during different steps of the purification procedures or resulting from modifications of cell culture conditions. In addition, this method was well suited to monitor the consistency of sialic acid distribution and to detect deamidation events occurring in accelerated stability studies. The i-cIEF method presented here provides an improvement over IEF slab gels in terms of resolution, automation and quantitation. Due to its exquisite resolution of narrow pI range, this technology can find applications in quality control environment as identity assay as well as in the analytical laboratory to monitor subtle modifications of the protein.

     

Chemical reactivity in matrix-assisted laser desorption/ionization mass spectrometry

During the control of a multistep organic synthesis on a soluble polymer (PEG) by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, a chemical reactivity was encountered when the matrix was acidic, for the samples where the amino moiety of the anchored compounds was protected as a Schiff base. Such imine hydrolysis was proven to be solely mediated by the acidic matrix during analyses since the expected protected structures were detected when the experiments were duplicated with a non-acidic matrix. Even if MALDI mass spectrometry was found to be more convenient than electrospray ionization mass spectrometry for the monitoring of liquid phase organic syntheses, the chemical reactivity imparted by the use of a matrix must be taken into account to avoid erroneous spectra interpretations. Copyright 1999 John Wiley & Sons, Ltd.