Aspects of antibody-catalyzed primary amide hydrolysis

Because there are many known C-terminally amidated peptides of biological importance, there is great potential in medicine and organic synthesis for antibodies that catalyze primary amide bond hydrolysis or formation. We characterized a catalytic antibody, 13D11, raised to a phosphinate hapten, that hydrolyzed the primary amide of a dansyl-alkylated derivative of (R)-phenylalaninamide (DNS-(R)F-NH₂). At pH 9.0, 13D11 hydrolyzed DNS-(R)F-NH₂ with a k_cat of 1.65 × 10^-7 s^-1 (k_cat/k_uncat = 132) and a K_m of 432 μM, and was stereospecifically hapten-inhibited (K_i = 14.0 μM). Control experiments indicated that the catalytic activity was not the result of a contaminating protease. In accordance with the hapten being a transition-state analog of base hydrolysis, the rate of DNS-(R)F-NH₂ hydrolysis increased with hydroxide concentration to an optimum pH of 9.5. Above pH 9.5, activity declined rapidly suggesting the antibody was inactivated during the long incubation period. This work demonstrates the feasibility of generating catalytic antibodies to hydrolyze unactivated amide bonds without cofactor assistance.     

Dyeing behaviour of lyocell fabric: effect of NaOH pre-treatment

To understand the effect of alkali pre-treatment on the dyeing of lyocell fabrics, samples are pre-treated with 0.0–7.0 mol dm⁻³ NaOH using a pad-batch process and then dyed with different types of reactive dyes. Exhaustion, fixation, and visual colour strength (K/S values) are measured. It is observed that sodium hydroxide pre-treatment significantly improves the colour yield, exhaustion, and fixation for all dyes used. Highest K/S values are obtained when the fabrics are pre-treated with 2.0–2.5 mol dm⁻³ NaOH. Cross-sectional analysis shows that below this optimum concentration the core fibres in the yarn are not dyed; at optimum concentration all fibres in yarn cross-section are homogeneously dyed. Cross-sectional analysis shows that as the pre-treatment concentration of NaOH increases above 2.5 mol dm⁻³, the fibres change progressively from a circular to angular cross-section, forming a solid unit. The decrease in K/S above the treatment concentration of 2.5 mol dm⁻³, though the %E and %F remains almost constant, is attributed to the distribution of dye over a larger surface area of the outer fibres in the yarn cross section, forcing the K/S at λ_max to decrease. This paper was presented at the 2nd International Cellulose Conference, Tokyo, Japan, 24th October 2007.     

Nitrite‐Templated Synthesis of Lanthanide‐Containing [2]Rotaxanes for Anion Sensing

The first anion‐templated synthesis of a lanthanide‐containing interlocked molecule is demonstrated by utilizing a nitrite anion to template initial pseudorotaxane formation. Subsequent stoppering of the interpenetrated assembly allows for the preparation of a lanthanide‐functionalized [2]rotaxane in high yield. Following removal of the nitrite anion template, the europium [2]rotaxane host is demonstrated to recognize and sense fluoride selectively.     

The synthesis of chiral periodic organosilica materials with ultrasmall mesopores

Helical organosilica materials were synthesized for the first time using a novel binaphthyl-based chiral co-monomer in less than 1?hour. The incorporation of a chiral co-monomer in the wall was shown to influence the curvature of the helical materials. As the amount of the chiral co-monomer was increased, the degree of curvature increased, illustrating the importance of this monomer to the overall morphology.     

Suzuki-Miyaura cross-coupling of aryl carbamates and sulfamates: experimental and computational studies

The first Suzuki-Miyaura cross-coupling reactions of the synthetically versatile aryl O-carbamate and O-sulfamate groups are described. The transformations utilize the inexpensive, bench-stable catalyst NiCl(2)(PCy(3))(2) to furnish biaryls in good to excellent yields. A broad scope for this methodology has been demonstrated. Substrates with electron-donating and electron-withdrawing groups are tolerated, in addition to those that possess ortho substituents. Furthermore, heteroaryl substrates may be employed as coupling partners. A computational study providing the full catalytic cycles for these cross-coupling reactions is described. The oxidative addition with carbamates or sulfamates occurs via a five-centered transition state, resulting in the exclusive cleavage of the aryl C-O bond. Water is found to stabilize the Ni-carbamate catalyst resting state, which thus provides rationalization of the relative decreased rate of coupling of carbamates. Several synthetic applications are presented to showcase the utility of the methodology in the synthesis of polysubstituted aromatic compounds of natural product and bioactive molecule interest.