Cellular logic with orthogonal ribosomes

The creation and use of unnatural molecules to control cellular function is a long standing goal of the chemical community, but in general, these efforts have been directed at finding molecules to inhibit or activate a particular molecular target or function, or to elicit a particular phenotype. Here we show that multiple unnatural molecules (orthogonal ribosomes) can be used combinatorially, in a single cell, to program Boolean logic functions. These experiments show how attention to the molecular specificity of noncovalent interactions between unnatural macromolecules allows the synthesis of complex function from the "bottom-up" in living matter.     

Nanoscale borromeates

[Structure: See text] In addition to a parent zinc(II) Borromean ring (BR) complex, the preparation and characterization of two hexasubstituted BR complexes with either 4-acetoxymethylphenyl or 4-methylthiophenyl substituents associated in turn with all six pyridyl rings has been achieved convergently in good yields by appealing to the dynamic features of the reactions between primary amino groups in a preformed acyclic ligand and 2,6-diformylpyridine. Two molecules of the acyclic ligands react with two molecules of 2,6-diformylpyridine to form a cyclic [2 + 2] tetraimine in the presence of Zn(II) ions as templates in 2-propanol at 70 degrees C. The successful preparation of the two derivatives by convergent template-directed syntheses opens up opportunities to self-assemble, under equilibrium control, numerous nanoscale metallo-organic particles with potentially useful properties.     

Heterocyclic derivatives of naphthalene-1,8-dicarboxylic anhydride. Part I. Nitro-7H-benzimidazo[2,1-a]benz[de]isoquinolin-7-ones

Condensation of o-phenylenediamine with 2-, 3- and 4-nitronaphthalene-1,8-dicarboxylic anhydrides gives, in each case, an isomer mixture. Separation of the mixtures into the six isomeric mononitro-7H-benzimidazo[2,1-a]benz[de]isoquinolin-7-ones is described and the isomers characterised in respect of previously reported data on some isomers; ir and mass spectrum data are reported, the latter showing fragmentation ions which may be used in characterising dyes based on this chromophore. Other new derivatives of 7H-benzimidazo[2,1-a]benz[de]isoquinolin-7-one are also described.     

Interannular communication in the radical anions of bis-cyclooctatetraene systems

[reaction: see text] The room-temperature potassium reduction of 1,2-bis-cyclooctatetraeneoxypropane yields two different regio-spin isomer anion radicals in equilibrium (COT-O-C(Me)HCH(2)CH(2)-O-COT(*)(-) = (*)(-)COT-O-C(Me)HCH(2)CH(2)-O-COT) that is shifted far to the right. The presence of the unreduced ring perturbs the spin density on the reduced ring. Addition of more electrons generates the diradical dianion ((*)(-)COT-O-C(Me)HCH(2)CH(2)-O-COT(*)(-)), and the anion radical on the secondary side splits the degeneracy of the psuedo-ortho protons of the anion radical on the primary side.     

Use of U-shaped donor-bridge-acceptor molecules to study electron tunneling through nonbonded contacts

A systematic determination of electronic coupling matrix elements in U-shaped molecules is demonstrated. The unique architecture of these systems allows for the determination of the electronic coupling through a pendant molecular moiety that resides between the donor and acceptor groups; this moiety quantifies the efficiency of electron tunneling through nonbonded contacts. Experimental electron-transfer rate constants and reaction free energies are used to calibrate a molecular-based model that describes the solvation energy. This approach makes it possible to experimentally determine electronic couplings and compare them with computational values.     

A highly emissive Cu2N2 diamond core complex supported by a [PNP]- ligand

A Cu2N2 diamond core structure, {(PNP)CuI}2 (2), supported by a [PNP]- ligand (1) ([PNP]- = bis(2-(diisobutylphosphino)phenyl)amide) has been prepared. 2 is highly emissive at ambient temperature in both the solid and solution states and is characterized by a relatively long-lived excited state (tau > 10 mus) and an unusually high quantum yield (phi > 0.65). These observations are consistent with a low degree of structural reorganization between the ground state of 2 and its excited state *2, and also with a high degree of steric protection of the two copper centers of 2 afforded by the bulky [PNP]- ligand. An estimate for the excited-state reduction potential of *2 (ca. -3.2 V vs Fc+/Fc), and the availability of two well-separated and reversible ground-state redox processes, suggests that bimetallic copper systems of these types may be interesting candidates to consider for photochemically driving multielectron redox transformations.     

Relaxivity and water exchange studies of a cationic macrocyclic gadolinium(III) complex

We conducted relaxometric and water exchange studies of the cationic [Gd((S,S,S,S)-THP)(H2O)]3+ complex (THP 1,4,7,10-tetrakis(2-hydroxy-propyl)-1,4,7,10-tetraazacyclododecane). While the NMRD profiles obtained are typical for DOTA-like complexes (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate), variable-temperature 7O NMR investigations revealed a relatively high water exchange rate (k(298)(ex) = 1.89 x 10(7) s(-1)). These results differ from those reported for other cationic tetraamide macrocyclic Gd(III) complexes, which exhibit characteristically low exchange rates. Since the low exchange rates are attributed partially to the geometry of the M isomer (square antiprismatic) in the tetraamide derivatives, the atypical water exchange rate observed in [Gd((S,S,S,S)-THP-(H2O)]3+ may result from a twisted square antiprismatic structure in this complex and from the relatively high steric strain at the water coordination site as a result of the presence of methyl groups at the alpha-position with respect to the Gd(III)-bound O atoms of THP.     

Studies on borate esters 1 : The ph dependence of the stability of esters of boric acid and borate in aqueous medium as studied by 11B NMR

The pH dependent stability of esters of boric acid and borate with glycol, glycolic acid, oxalic acid and glyceric acid as dihydroxy compounds has been studied. ¹¹B NMR provides a suitable analytical tool for the quantitative determination and structure elucidation of the various esters in aqueous medium. The pH dependent stability of esters of boric acid and borate is formulated in a general rule of thumb: esters of boric acid and borate with dihydroxy compounds in aqueous medium show the highest stability at that pH where the sum of the charges of the free esterifying species is equal to the charge of the ester.     

Stable Methods for Evaluating the Points cos(i{pi}/n)

A variety of alternative methods for evaluating cos(i/n) fori= 0, 1,...,n are compared theoretically and experimentally,and the best ones selected on the basis of accuracy and thecomputational efficiency. The error analysis involved demonstrateshow certain mathematically equivalent recurence relations canexhibit very different computational behaviour.