N-Benzoyl-L-methioninol

Microplate assays with 96 wells were optimized to screen proteolytic activities in mite homogenates. Whole-mite extracts of Acarus siro, Aleuroglyphus ovatus, Tyrophagus putrescentiae, Tyroborus lini, Carpoglyphus lactis, Lepidoglyphus destructor, and Dermatophagoides farinae exhibited non-specific proteolytic activity in buffers from pH 2 to 12, and three peaks of highest activity at pH 3, 5-6, and 10 were distinguished. The reducing agent Tris(2-carboxyethyl)phosphine hydrochloride decreased general proteolytic activity on azocasein at pH 5 and 6. The results obtained on two non-specific substrates, azocasein and azoalbumin, showed highly different ranks of the species at pH 5 and 6. Proteolytic activities toward N(α)-Benzoyl-D,L-arginine 4-nitroanilide hydrochloride, N-Succinyl-L-alanyl-L-alanyl-L-prolyl-L-phenylalanine 4-nitroanilide, N-Succinyl-L-alanyl-L-alanyl-L-alanine 4-nitroanilide, Benzyloxycarbonyl-L-arginine-L-arginyl 4-nitroanilide, and N-Methoxysuccinyl-L-alanyl-L-alanyl-L-prolyl-L-methionine 4-nitroanilide (MAAPMpNA) were highest at alkaline pH, but the activity toward MAAPMpNA was also high at pH 5 and 6. In contrast, N-Succinyl-L-alanyl-L-alanyl-L-phenylalanine 4-nitroanilide (AAPpNA) and L-arginyl 4-nitroanilide (ArgpNA) had the highest activity recorded at pH 6. The high activities observed on AAPpNA, ArgpNA, and MAAPMpNA at digestive pH suggest that enzymes present in these extracts could have the majority of proteolysis in the mite gut. Evidence of the presence of proteolytic activities on all tested substrates and in all the tested mite homogenates suggests that the proteolytic activities may contribute to allergenicity. Poor or undetected hydrolytic activities of mite extracts toward substrates for keratin and collagen at digestive pH underline the importance of ecological interactions between mites and microorganisms in the utilization of such substrates.

Laser-coupled microphotoreactors were developed to bubble singlet oxygen [(1)O(2) ((1)Δ(g))] into an aqueous solution containing an oxidizable compound. The reactors consisted of custom-modified SMA fiberoptic receptacles loaded with 150 μm silicon phthalocyanine glass sensitizer particles, where the particles were isolated from direct contact with water by a membrane adhesively bonded to the bottom of each device. A tube fed O(2) gas to the reactor chambers. In the presence of O(2), singlet oxygen was generated by illuminating the sensitizer particles with 669 nm light from an optical fiber coupled to the top of the reactor. The generated (1)O(2) was transported through the membrane by the O(2) stream and formed bubbles in solution. In solution, singlet oxygen reacted with probe compounds (9,10-anthracene dipropionate dianion, trans-2-methyl-2-pentanoate anion, N-benzoyl-D,L-methionine, or N-acetyl-D,L-methionine) to give oxidized products in two stages. The early stage was rapid and showed that (1)O(2) transfer occurred via bubbles mainly in the bulk water solution. The later stage was slow; it arose only from (1)O(2)-probe molecule contact at the gas/liquid interface. A mechanism is proposed that involves (1)O(2) mass transfer and solvation, where smaller bubbles provide better penetration of (1)O(2) into the flowing stream due to higher surface-to-volume contact between the probe molecules and (1)O(2).

Traditionally, Type II heterogeneous photo-oxidations produce singlet oxygen via external irradiation of a sensitizer and external supply of ground-state oxygen. A potential improvement is reported here. A hollow-core fiber-optic device was developed with an "internal" supply of light and flowing oxygen, and a porous photosensitizer-end capped configuration. Singlet oxygen was delivered through the fiber tip. The singlet oxygen steady-state concentration in the immediate vicinity of the probe tip was ca 20 fm by N-benzoyl-DL-methionine trapping. The device is portable and the singlet oxygen-generating tip is maneuverable, which opened the door to simple disinfectant studies. Complete Escherichia coli inactivation was observed in 2 h when the singlet oxygen sensitizing probe tip was immersed in 0.1 mL aqueous samples of 0.1-4.4 x 10(7) cells. Photobleaching of the probe tip occurred after ca 12 h of use, requiring baking and sensitizer reloading steps for reuse.