Methods for detection of point mutations: performance and quality assessment. The IFCC Scientific Division, Committee on Molecular Biology Techniques.

We give an overview of current methods for the detection of point mutations as well as small insertions and deletions in clinical diagnostics. For each method, the following characteristics are specified: (a) principle, (b) major modifications, (c) maximum fragment size that can be analyzed, (d) ratio and type of mutations that can be detected (e) minimum ratio of mutant to wild-type alleles at which mutations can be detected, and (j) detection methods. Special attention is paid to the possibilities of quality assessment and the potential for standardization and automation.     

Thermally reversible polymer linkages. II. Linear addition polymers

The stepwise addition polymerization reactions of bisazlactones [bis(2-oxazolin-5-one)s] and a variety of 4,4′-bisphenols have been studied for the purpose of making thermally reversible linear polymers. Thus polymerization occurs at or near room temperature, while depolymerization yielding the two monomer species occurs at elevated temperatures. The synthesis of oligomers in solution without the use of catalyst occurs for the reaction of bisazlactones with bisphenols containing an electron-withdrawing moiety between the two phenol groups of the bisphenol. These oligomers regenerate the bisphenol and bisazlactone monomers upon heating to 165–200°C for several hours under dry box conditions. In many cases, these reactions follow the same patterns of reactivity observed in model studies. This chemistry may be useful for forming degradable or recyclable polymers, where shortchain prepolymers, or macromonomers, endcapped with azlactone and phenol moieties could be used to form high molecular weight polymers that are thermoreversible. Such a reaction system might also be used for preventing reactions of bisphenols and/or bisazlactones at low temperatures, with the desired reaction initiated by formation of the reactive species at elevated temperatures. Envisioned uses in this case might be thermally triggered crosslinking or polymerization reactions, or temperature controlled drug release. © 1993 John Wiley & Sons, Inc.     

Mechanistic studies of chelating resins using two-phase potentiometry

The elucidation of metal ion binding mechanisms with chelating resins by treating the resin as a collection of monomeric units is an established approach. In this paper, this approach is used to treat data obtained from two-phase potentiometric titrations by the programme ESTA. Apparent protonation and formation constants could be calculated. From these, species distribution plots could be obtained. These, in turn, allowed the calculation of the more familiar distribution ratios. The method was tested on Fe(III) and Nd(III) bonding with the iminodiacetate functionalized resin, Chelex 100; and Ca(II) bonding to the aminomethylphosphonate functionalized resin, Purolite S940. Good results were obtained indicating the applicability of this method. Comparisons with the literature are made.     

Synthesis and thermal crosslinking of carbosiloxane and oligo(oxyethylene) polymers

Acyclic diene metathesis (ADMET) polymerization has been used in the synthesis of telechelic materials using alkoxy‐functionalized carbosiloxane or oligo(oxyethylene)‐based polymers, varying from internal to terminal cured materials or the combination of them. Previous investigations demonstrated that introduction of chain‐end crosslinking improves the stress–strain behavior of such materials. A series of saturated and unsaturated carbosiloxane and oligo(oxyethylene)‐based polymers were synthesized by ADMET polymerization using silacyclobutane as chain‐end, thermally induced crosslinker. The carbosiloxane derivatives presented pure amorphous behavior, whereas the oligo(oxyethylene) polymers were semicrystalline. The thermal curing process was monitored by differential scanning calorimetry via the exotherm between 160 and 210 °C. Mechanical properties on thermoset polymers were measured, where cured polymers showed moduli from 0.6 to 9.3 MPa, tensile strengths from 0.3 to 1.0 MPa, and elongations from 12 to 76%. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Physical fabrication of colloidal ZnO nanoparticles combining wet-grinding and laser fragmentation

Combination of wet-grinding and laser fragmentation is a promising approach to advance both methods: Laser fragmentation will be more efficient when combined with mechanical treatment and wet-grinding may take advance of the abrasion-free laser process to achieve fabrication of smaller particles. By mechanical pre-treatment of zinc oxide microparticles in a stirred-media mill, the starting material is activated by generation of crystallographic defects, which strongly enhance the efficiency of subsequent laser fragmentation. Picosecond-laser irradiation of mechanically treated and untreated microparticles suspended in water yielded in colloidal zinc oxide nanoparticles. Furthermore, nanoparticle productivity and properties can be controlled by variation of anionic surfactant concentration.     

Magtrieve™: a convenient catalyst for the oxidation of alcohols

We find that Magtrieve™ (CrO₂) catalyzes the oxidation of a wide variety of alcohols with periodic acid as the terminal oxidant. Mild conditions, short reaction times, and facile aqueous work-up make this a most attractive method. Olefins are not oxidized under these conditions; thus alcohols react selectively in the presence of alkenes. Conditions have been optimized with respect to catalyst loading, solvent, and co-oxidant; and the scope of the reaction includes primary and secondary benzylic, allylic, and aliphatic alcohols.     

Synthesis and characterization of a chlorofunctionalized unsaturated carbosilane oligomer

Acyclic diene metathesis (ADMET) polymerization offers a viable route for the synthesis of chlorofunctionalized unsaturated carbosilane oligomers. The Si Cl bond in unsaturated carbosilane monomers remains inert during metathesis and the use of a highly reactive molybdenum-based, Lewis acid-free alkylidene catalyst affords unsaturated chlorofunctionalized carbosilane oligomers with known vinyl end groups. The first synthesis of an unsaturated carbosilane oligomer functionalized with a Si Cl bond was performed. A chlorofunctionalized silacyclopentene product was also observed, due to a backbiting reaction. This new class of functionalized oligomers has a low glass transition temperature and sites of unsaturation which may be used for further reaction. ADMET chemistry now provides access to a variety of chlorofunctionalized unsaturated carbosilanes which can be used to tailor make hydrolytically stable carbosilane oligomers and polymers via nucleophilic grafting reactions.     

Acyclic diene metathesis (ADMET) depolymerization: The synthesis of 1,4-polybutadiene telechelics

ADMET depolymerization is a viable route in the formation of tailored-molecular-weight polybutadiene telechelics. The bulk depolymerization requirement is met by initially forming macrocyclic butadiene, thereby decreasing the amount of macrocyclic formation. This synthetic scheme is capable of generating well-defined, tailored-molecular-weight polybutadiene telechelics (M̄_n = 2600).     

An examination of the substitution chemistry of di-n-hexyldichlorosilane

Various nucleophiles were reacted with the substrate di-n-hexyldichlorosilane as model reactions for the substitution of two geminal Si---Cl bonds on polymer backbone repeat units. The reactants examined were chosen on the basis of steric bulk, electronic factors, and resulting stability of the product. Linear and branched alcohol nucleophiles used in conjunction with an amine proton acceptor produced disubstituted products in moderate yields, whereas bulkier reagents substituted only one silicon---chlorine bond. Due to their vastly increased nucleophilicity, alkyllithium reagents were found to have increased activity and were found to produce very high yields.