Direct coupling of polymer-based microchip electrophoresis to online MALDI-MS using a rotating ball inlet

We report on the coupling of a polymer-based microfluidic chip to a MALDI-TOF MS using a rotating ball interface. The microfluidic chips were fabricated by micromilling a mold insert into a brass plate, which was then used for replicating polymer microparts via hot embossing. Assembly of the chip was accomplished by thermally annealing a cover slip to the embossed substrate to enclose the channels. The linear separation channel was 50 microm wide, 100 microm deep, and possessed an 8 cm effective length separation channel with a double-T injector (V(inj) = 10 nL). The exit of the separation channel was machined to allow direct contact deposition of effluent onto a specially constructed rotating ball inlet to the mass spectrometer. Matrix addition was accomplished in-line on the surface of the ball. The coupling utilized the ball as the cathode transfer electrode to transport sample into the vacuum for desorption with a 355 nm Nd:YAG laser and analyzed on a TOF mass spectrometer. The ball was cleaned online after every rotation. The ability to couple poly(methylmethacrylate) microchip electrophoresis devices for the separation of peptides and peptide fragments produced from a protein digest with subsequent online MALDI MS detection was demonstrated.     

EFFECT OF CHLORIDE AND BENZOATE ANIONS ON THE DELAYED LIGHT EMISSION IN DCMU-TREATED SPINACH CHLOROPLASTS

Abstract —Chloride anions, when added to DCMU [3-(3,4-dichlorophenyl)-1,1-dimethylurea]-treated spinach chloroplasts, change the rate of decay of the delayed light emission in the seconds region but do not change the shape or the temperature dependence of the decay. Benzoate anions, on the other hand, change both the rate and the shape of the decay of the delayed light emission. These results are consistent with a model in which the membrane potential and the structure of the reaction center affect the decay kinetics of the delayed light emission in the seconds region.     

Persistent (amino)(silyl)carbenes

(Amino)(silyl)carbenes, prepared by substitution reactions at a carbene center, can survive several days at 0 degrees C. These species are not push-pull carbenes as their phosphino analogues and therefore are excellent ligands for transition-metal centers.     

Validation studies and proficiency testing

Genetically modified organisms (GMOs) entered the European food market in 1996. Current legislation demands the labeling of food products if they contain <1% GMO, as assessed for each ingredient of the product. To create confidence in the testing methods and to complement enforcement requirements, there is an urgent need for internationally validated methods, which could serve as reference methods. To date, several methods have been submitted to validation trials at an international level; approaches now exist that can be used in different circumstances and for different food matrixes. Moreover, the requirement for the formal validation of methods is clearly accepted; several national and international bodies are active in organizing studies. Further validation studies, especially on the quantitative polymerase chain reaction methods, need to be performed to cover the rising demand for new extraction methods and other background matrixes, as well as for novel GMO constructs.     

Deprotonation of chloropyridines using lithium magnesates

4-Chloropyridine was deprotonated on treatment with 1/3 equiv of the highly coordinated magnesate Bu₃(TMP)MgLi₂ in THF at −10 °C, as evidenced by trapping with I₂. The use of Bu(TMP)₂MgLi in Et₂O allowed the reaction of 2-chloropyridine, giving the 3-functionalized derivative as the main product. Mixtures of 3- and 4-functionalized derivatives were obtained when 2,6-dichloropyridine was involved in the reaction. Performing the reaction on 3-chloropyridine with lithium magnesates in THF, either the 4,4′-dimer or the 4-iodo derivative was formed after quenching by I₂, the former using 1/3 equiv of Bu₂(TMP)MgLi and the latter using 1 equiv of (TMP)₃MgLi. Similar results were observed with 3,5-dichloropyridine, 2,5-dichloropyridine and 3-chloro-2-fluoropyridine. 1,2-Migration of the lithium arylmagnesate formed by deprotonation was proposed to justify the dimers formation.     

Synthesis and 1H NMR study of 3,4-di ethyl-1,2,3,3a,4,5-hexahydro-canthinone-6

The racemic mixtures of the two epimers of 3,4-diethyl-l,2,3,3a,4,5-hexahydro-canthinone-6 (3,4-diethyl-2,3,3a,4,5,6-hexahydro-6-oxo-1H-indolo-(3,2,1 ,de) (1,5)naphtyridine) have been prepared. They were separated by crystallization of one of the synthesis intermediates. Identification of the configuration was possible by 1h NMR spectroscopy after running a 2D J-resolved spectrum of the “cis”-isomer.     

New polyphenylquinoxalines linked by m-terphenyl flexibilizing groups

Three new monomers with phenylglyoxyloyl groups fixed on the 4,4′-, 4,6′-, and 4,4″-positions of m-terphenyl were synthesized by different pathways. They were used to prepare a series of polyphenylquinoxalines by solution polycondensation with 3,3′-diaminobenzidine and 3,3′,4,4′-tetraaminodiphenyl ether. These polymers exhibited excellent oxidative and thermal stability as shown by thermogravimetric analysis and isothermal aging in circulating air between 300 and 450°C. Clear yellow films, cast from m-cresol solution, were used to measure their softening temperature by thermomechanical analysis (TMA). Numerical data thus obtained, indicated a thermoplastic behavior in the temperature range 300 ± 15°C. Crosslinking of the linear polymers by isothermal heat exposure under argon between 300 and 500°C was investigated by means of TMA. Molded materials were fabricated under constant pressure (996 psi) at 500–525°C with an Instron testing machine. These polymers were also used for preliminary evaluation as matrices for 181-E glass reinforced composites. Flexural values obtained after isothermal aging in air up to 400°C indicated a potential use varying from 150 hr at 350°C to 24 hr at 400°C.     

X-ray crystal structures of three nonbenzodiazepinic ligands for the benzodiazepine receptor sites: SR95926, CMW1842, and L16317:nab initio MO study of the electronic properties

The crystal structures ofp-methoxyphenyl-3-triazolo [4,3-a] isoquinoline (SR95926),p-methoxyphenyl-3-triazolophtalazine (CMW1842), andp-methoxyphenyl-3-N-dimethoxyethylamino-6-triazolophtalazine (L16317) have been solved by direct methods from single-crystal X-ray diffraction data, and refined by full-matrix least squares. SR95926: monoclinic,P2₁/n,a=20.950(3),b=6.769(1),c=9.465(2) Å,=100.90(1)°. CMW1842: triclinic,P¯1,a=8.784(1),b=9.160(4),c=8.555(1) Å,=99.10(2),=93.90(1), =106.77(1)°. L16317: monoclinic,P2₁/_n,a=20.124(3),b=9.586(1),c=10.788(1) Å,=91.91(1)°. FinalR factors are 0.034, 0.037, and 0.053, respectively. Experimental geometries were used to perform STO-3Gab initio molecular-orbital calculations. A relationship between the electronic pattern within the molecules and the affinity of the benzodiazepine receptor sites is pointed out.     

Quasi-convex sets and size × curvature condition,application to nonlinear inversion

We define a family of sets of a Hilbert space (quasi-convex sets) on which a generalization of the usual theory of projection on convex sets can be defined (existence, uniqueness, and stability of the projection of all points of some neighborhood of the set). We then give a constructive sufficient condition, called the size × curvature condition, for a setD to be quasi-convex, which involves radii of curvatures of curves lying on the setD. Finally, we use the above result for the study of nonlinear least-squares problems, as they appear in parameter estimation, for which we give a sufficient condition ensuring existence, uniqueness, and stability.