Immobilization of uricase in layer-by-layer films used in amperometric biosensors for uric acid

The layer-by-layer technique was exploited to immobilize the enzyme uricase onto indium tin oxide substrates coated with a layer of Prussian Blue. Uricase layers were alternated with either poly(ethylene imine) or poly(diallyldimethylammoniumchloride), and the resulting films were used as amperometric biosensors for uric acid. Biosensors with optimum performance had a limit of detection of 0.15 μA μmol l⁻¹ cm⁻² with a linear response between 0.1 and 0.6 μM of uric acid, which is sufficient for use in clinical tests. Bioactivity was preserved for weeks, and there was negligible influence from interferents, as detection was carried out at 0.0 V vs saturated calomel electrode. This paper is dedicated to the memory of Francisco C. Nart.     

Microwave-assisted synthesis and antimicrobial activity of 5-trihalomethyl-3-arylisoxazoles

A series of twelve 5-trihalomethyl-3-arylisoxazoles was synthesized and screened for antibacterial and antifungal activities. The compounds were synthesized from the cyclondensation of 1,1,1-trihalo-4-alkoxy-3-alken-2-ones [CX ₃C(O)C(R ²)=C(R ¹)OR, where X = Cl and F; R=Me; R ²=H; R ¹=H, Me, F, Cl, Br, and NO₂] with hydroxylamine hydrochloride through a rapid one-pot reaction via microwave irradiation. Some of the 5-trihalomethyl-3-arylisoxazoles exhibited good in vitro anti-Cryptococcus activity. Correspondence: Marcos A. P. Martins, Núcleo de Química de Heterociclos (NUQUIMHE), Centro de Ciências Naturais e Exatas, Departamento de Química, Universidade Federal de Santa Maria, 97.105-900 Santa Maria, RS, Brazil.     

Synthesis and antimicrobial evaluation of coordination compounds containing 2,2′-bis(3-aminopyridyl) diselenide as ligand

The reaction between 2,2′-bis(3-aminopyridyl) diselenide (L) and metal transition salts results in the formation of molecular or cluster complexes. The structural elucidation of the synthesized complexes [CuCl₂(L)] ( 1 ), [Cu(3-NH₂PySeO₂)₂]·2H₂O ( 2 ), [Cu₄(3-NH₂PySe)₄]·dimethylformamide ( 3 ), [CoCl₂(L)] ( 4 ), [ZnCl₂(L)] ( 5 ), and [Ag₆(3-NH₂PySe)₆] ( 6 ) demonstrates the coordination of nitrogen atoms to Cu^II, Co^II, and Zn^II, and that of the selenium atoms to Cu^I and Ag^I, which agrees with Pearson’s hard and soft acids and bases (HSAB) theory. Furthermore, the oxidation of selenium with the formation of 3-aminopyridylseleninate [3-NH₂PySeO₂]⁻ bonded to the copper atom was observed in complex 2 . The antimicrobial action of complexes 1 , 2 , 4 , and 5 was evaluated against Mycobacterium fortuitum, Mycobacterium massiliense, and Mycobacterium abscessus. It was observed that all these complexes have potential antimicrobial activity compared with the free ligand and metal salts used in the synthesis.     

An efficient and regiospecific preparation of trifluoromethyl substituted 4‐( 1H‐pyrazol‐1 ‐yl)‐7‐chloroquinolines

A new series of 4‐[3‐alkyl(aryl)(heteroaryl)‐5‐hydroxy‐5‐trifluoromethyl‐4,5‐dihydro‐1H‐pyrazol‐1‐yl]‐7‐chloroquinolines, where [alkyl = CH₃; aryl = C₆H₅, 4‐CH₃C₆H₄, 4‐FC₆H₄, 4‐ClC₆H₄, 4‐BrC₆H₄, 4‐CH₃OCgH₄, 4‐NO₂CgH₄, 4‐biphenyl, 1‐naphthyl; heteroaryl = 2‐furyl and 2‐thienyl] has been regiospecifi‐caly obtained from the reaction of 7‐chloro‐4‐hydrazinoquinoline with 4‐substituted‐l,1,1‐trifluoro‐4‐methoxybut‐3‐en‐2‐ones in 61 ‐ 96 % yield. Subsequently, dehydration reaction of 4,5‐dihydropyra‐zolylquinolines under acid conditions furnished a new series of 4‐(3‐substituted‐5‐trifluoromethyl‐1H‐pyra‐zol‐1‐yl)‐7‐chloroquinolines in 73 ‐ 96 % yield.     

Dynamic condensation of water at crack tips in fused silica glass

Water molecules play a fundamental role in the physics of slow crack propagation in glasses. It is commonly understood that, during stress-corrosion, water molecules that move in the crack cavity effectively reduce the bond strength at the strained crack tip and, thus, support crack propagation. Yet the details of the environmental condition at the crack tip in moist air are not well determined. In a previous work, we reported direct evidence of the presence of a 100 nm long liquid condensate at the crack tip in fused silica glass during very slow crack propagation (10^?9–10^?10 m/s). These observations are based on in situ AFM phase imaging techniques applied on DCDC glass specimens in controlled atmosphere. Here, we discuss the physical origin of the AFM phase contrast between the liquid condensate and the glass surface in relation to tip-sample adhesion induced by capillary bridges. We then report new experimental data on the water condensation length increase with relative humidity in the atmosphere. The measured condensation lengths were much larger than what predicted using the Kelvin equation and expected geometry of the crack tip.     

One‐pot synthesis of aryl and heteroaroyl‐substituted hydroxypyrazolines from the reactions of β‐alkoxyvinyl trichloromethyl ketones with heteroarylhydrazides

The one‐step regiospecific synthesis of a novel series of 10 trichloromethyl‐, aryl‐, and heteroaroyl‐substituted 5‐hydroxy‐2‐pyrazolines affords 1‐(2‐thenoyl)‐, 1‐(2‐furoyl)‐, and 1‐(isonicotinoyl)‐3‐aryl‐5‐hydroxy‐5‐trichloromethyl‐4,5‐dihydro‐1H‐pyrazoles in 63–92% yields from the cyclocondensation reactions of 1,1,1‐trichloro‐4‐methoxy‐4‐aryl‐3‐buten‐2‐ones (where aryl substituents are –C₆H₅, 4‐CH₃C₆H₄, 4‐OCH₃C₆H₄, 4‐FC₆H₄, 4‐ClC₆H₄, 4‐BrC₆H₄) with 2‐thiophenecarboxylic hydrazide, furoic hydrazide, and isonicotinic acid hydrazide, respectively. Dehydration reaction of two 2‐pyrazolines with P₂O₅ furnished the corresponding 1H‐pyrazoles in low yields (21–29%). © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:685–691, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20261     

Measurement of hyperfine splitting in the OH radical by a radio-frequency microwave double resonance method

The RFMDR technique is used to investigate the hydroxyl radical spectrum. The experiment allows to analyse the magnetic hyperfine structure for J = 7/2 and 9/2 in the ²Π_3/2 state and gives more complete and accurate results than in previous works.     

Columnar mesomorphism of bent-rod mesogens containing 1,2,4-oxadiazole rings

In this study, the synthesis, characterization, and mesomorphic properties of ten new bent-rod compounds containing two units of 1,2,4-oxadiazoles are reported. In order to understand the relationship between the structure and the mesomorphic behavior, molecules containing a variety of polar substituents (i.e., I, NO₂, NH₂, OH) on the central rigid core were prepared. The hexagonal columnar mesomorphism was characterized by DSC and POM and the nature of the mesophases was established through XRD studies. The driving force for self-assembly can be explained by microsegregation between the aliphatic parts and the polar parts, producing a dimer, trimer, and tetramer inside a single disc.