Porous Biodegradable Scaffold: Predetermined Porosity by Dissolution of Poly(ester‐anhydride) Fibers from Polyester Matrix

A novel selective leaching method for the porogenization of the biodegradable scaffolds was developed. Continuous, predetermined pore structure was prepared by dissolving fast eroding poly(ε‐caprolactone)‐based poly(ester‐anhydride) fibers from the photo‐crosslinked poly(ε‐caprolactone) matrix. The porogen fibers dissolved in the phosphate buffer (pH 7.4, 37 °C) within a week, resulting in the porosity that replicated exactly the single fiber dimensions and the overall arrangement of the fibers. The amount of the porosity, estimated with micro‐CT, corresponded with the initial amount of the fibers. The potential to include bioactive agents in the porogen fibers was demonstrated with the bioactive glass.

     

Improved surface stability and biotin binding properties of streptavidin coating on polystyrene

The ultimate nature of streptavidin to bind biotin tightly is widely utilized in many solid-phase based applications to provide a universal binding surface for biotinylated molecules. However, the preparation of the streptavidin coatings by passive adsorption may heavily alter the binding properties of native streptavidin and may not result in the best possible capture surface for demanding solid-phase assays. By introducing sulphydryl groups through primary amines in the protein, we have activated and conjugated native streptavidin into larger protein polymers resulting in high local binding density when coated on polystyrene. This thiolated streptavidin formed through chemical modification has improved adsorption properties and biotin binding capability, compared to the native streptavidin. When this thiolated streptavidin is coated on polystyrene, a dense surface is formed, which provides up to 3-fold increase in the biotin binding efficiency and improves the surface stability by minimizing the desorption of the adsorbed protein from the surface during incubation. Furthermore, this high-capacity surface is resistant to harsh chemical treatments, such as denaturing conditions or mild reducing conditions. The improved adsorption properties of the thiolated streptavidin allow the coating process to be performed with shorter incubation times (15 min), still providing enhanced solid-phase properties, compared to a reference streptavidin surface.     

Fluorine-free organoxenon chemistry: HXeCCH,HXeCC, and HXeCCXeH

Three novel Xe-containing organic compounds, HXeCCH, HXeCC (open-shell species), and HXeCCXeH, are identified using infrared absorption spectroscopy. They are prepared in a low-temperature Xe matrix using UV photolysis of acetylene and subsequent annealing at 40-45 K. The experimental observations are supported by extensive ab initio calculations. This work demonstrates a new way to activate the H-Ctbd1;C- group without use of XeF(2), which can extend the range of organoxenon compounds.     

Search for B+/--->[K(-/+)pi(+/-)](D)K+/- and upper limit on the b-->u amplitude in B+/--->DK+/-

We search for B+/--->[K(-/+)pi(+/-)](D)K+/- decays, where [K(-/+)pi(+/-)](D) indicates that the K-/+pi(+/-) pair originates from the decay of a D0 or D (0). Results are based on 120x10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at SLAC. We set an upper limit on the ratio R(Kpi) identical with[Gamma(B+-->[K(-)pi(+)](D)K+)+Gamma(B--->[K(+)pi(-)](D)K-)][Gamma(B+-->[K(+)pi(-)](D) / K+)+Gamma(B--->[K(-)pi(+)](D)K-)]<0.026 (90% C.L.). This constrains the amplitude ratio r(B) identical with|A(B--->D 0K-)/A(B--->D0K-)|<0.22 (90% C.L.), consistent with expectations. The small value of r(B) favored by our analysis suggests that the determination of the Cabibbo-Kobayashi-Maskawa phase gamma from B-->DK will be difficult.     

Measurements of CP-violating asymmetries in B0-->K(0)(s)pi(0) decays

We present a measurement of the time-dependent CP-violating (CPV) asymmetries in B0-->K(0)(S)pi(0) decays based on 124x10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. In a sample containing 122+/-16 signal decays, we obtain the magnitudes of the direct CPV asymmetry CK(0)(S)(pi(0))=0.40(+0.27)(-0.28)+/-0.09 and of the CPV asymmetry in the interference between mixing and decay SK(0)(S)(pi(0))=0.48(+0.38)(-0.47)+/-0.06 where the first error is statistical and the second systematic.     

The Near Resolvable 2-(13, 4, 3) Designs and Thirteen-Player Whist Tournaments

A -player whist tournament is a schedule of games, where in each round the players are partitioned into games of four players each with at most one player left over. In each game two of the players play as partners against the other two. All pairs of players must play in the same game exactly three times during the tournament; of those three times, they are to play as partners exactly once. Whist tournaments for players are known to exist for all 0,1 (mod 4). The special cases of directed whist tournaments and triplewhist tournaments are known to exist for all sufficiently large , but for small several open cases remain. In this paper we introduce a correspondence between near resolvable 2-(, k, designs and a particular class of codes. The near resolvable 2-(13, 4, 3) designs are classified by classifying the corresponding codes with an orderly algorithm. Finally, the thirteen-player whist tournaments are enumerated starting from the near resolvable 2-(13, 4, 3) designs.Both authors were supported by Helsinki Graduate School in Computer Science and Engineering (HeCSE). In addition, the first author was supported by a grant from the Nokia Foundation and the second author by a grant from the Foundation of Technology, Helsinki, Finland (Tekniikan Edistämissäätiö).AMS classification: primary 05B05, secondary 05B30, 05-04, 94B25     

Chemical compounds formed from diacetylene and rare-gas atoms: HKrC4H and HXeC4H

New organic rare-gas compounds, HRgC4H (Rg = Kr or Xe), are identified in matrix-isolation experiments supported by ab initio calculations. These compounds are the largest molecules among the known rare-gas hydrides. They are prepared in low-temperature rare-gas matrixes via UV photolysis of diacetylene and subsequent thermal mobilization of H atoms at approximately 30 and 45 K for Kr and Xe, respectively. The strongest IR absorption bands of the HRgC4H molecules are the H-Rg stretches with the most intense components at 1290 cm(-1) for HKrC4H and at 1532 cm(-1) for HXeC4H, and a number of weaker absorptions (C-H stretching, C-C-C bending, and C-C-H bending modes) are also found in agreement with the theoretical predictions. As probably the most important result, the IR absorption spectra indicate some further stabilization of the HRgC4H molecules as compared with the corresponding HRgC2H species identified recently (Khriachtchev et al. J. Am. Chem. Soc. 2003, 125, 4696 and Khriachtchev et al. J. Am. Chem. Soc. 2003, 125, 6876). The computational energetic results support this trend. HXeC4H is predicted to be 2.5 eV lower in energy than H + Xe + C4H, which is approximately 1 eV larger than the corresponding value for HXeC2H. We expect that the larger molecules HRgC6H and HRgC8H are even more stable and the HRgC2nH species are good candidates for bulk organic rare-gas material.     

Synthesis of Lanthanide(III) Chelates by Using ‘Click’ Chemistry

The copper(I)‐catalyzed dipolar [2+3] cycloaddition reaction of an azide and a terminal alkyne is exploited in the preparation of various europium(III), terbium(III), and dysprosium(III) chelates (Schemes 1–3). By changing the nature of the alkyne and the azide, a wide range of chelates and biomolecule‐labeling reactants were obtained. The photophysical properties (Table) of the synthesized chelates are also discussed.     

Luminescence of Europium(III) Chelates with 4-(Arylethynyl)pyridines as Ligands

Some Spectral properties and luminescence intensities of Eu^III chelates with 4-(arylethynyl)pyridine-2,6-dicarboxylic acids 1 – 15 and 2,2′,2″,2′″-{[4-(arylethynyl)pyrridine-2,6-diyl]bis(methylenenitrilo)} tetrakis(acetic acids) 16 – 26 were measured both in H₂O and EtOH solutions for the purpose of developing suitable labels to be used in time-resolved luminescence-based bioaffinity assays (Tables 1 and 2). The substitution at the Ar group has a significant effect upon the observed luminescence intensities, excitation wavelengths, and decay constants of the complexes, Moreover, the changes in the environment cause great variation in those properties of certain Eu^III chelates.     

An Orthogonally Protected alpha,alpha-bis(aminomethyl)-beta-alanine building block for the construction of glycoconjugates on a solid support

Synthetic glycoclusters are extensively used as mimetics of naturally occurring, multivalent carbohydrate ligands in various glycobiological applications. Their preparation, however, is far from trivial, and it still is a limiting factor in the study of carbohydrate binding. We herein report the synthesis of an orthogonally protected building block, N-Alloc-N'-Boc-N' '-Fmoc-alpha,alpha-bis(aminomethyl)-beta-alanine (1), and its use in the preparation of triantennary peptide glycoclusters (21-24) on a solid support. The assembly of the clusters involves removal of the amino protections of the solid-supported branching unit 1 in the order Fmoc, Boc, and Alloc, and subsequent coupling of peracetylated O-(glycopyranosyl)-N-Fmoc-L-serine pentafluorophenyl esters (galactose, glucose, mannose, and ribose) to each amino group exposed.