The terahertz (THz) absorption spectra of 4- and 5-hydroxysalicylic acid were measured by terahertz time-domain spectroscopy (THz-TDS) in the range of 0.4-2.8 THz. The unit cells of both were calculated by density functional theory (DFT), and the theoretical simulation and experimental data were basically in agreement. To further interpret the origin of the characteristic absorption peaks, vibration characteristics and interactions of the unit cell model were analyzed by using potential energy distribution (PED) and interaction region indicator (IRI) method. The analysis indicated that the absorption peaks of 4- and 5-hydroxysalicylic acid were mainly derived from the vibration mode of dihedral angle torsion, and were closely related to the hydrogen bonds. And the intermolecular weak interaction of both were mainly dominated in quantity by van der Waals interaction. The results show that this is an effective solution to identify isomers and explain the formation mechanism of characteristic absorption peaks by using THz-TDS and combining PED and IRI methods.

Neste artigo, foi desenvolvido um novo método fluorométrico, simples, sensível e seletivo, para a medição de tripsina em amostras biológicas. O método foi baseado na medição da supressão da intensidade da fluorescência de agregados de nanopartículas de ouro estabilizados com albumina sérica bovina (BSA), pela proteólise enzimática. A curva de calibração para tripsina foi atingida no intervalo de concentração de 1-60 nmol L-1 com coeficiente de correlação 0,995 e um limite de detecção de 0,6 nmol L-1. O método foi também usado satisfatoriamente para avaliação da atividade da tripsina e os resultados mostraram que os valores das constantes de Michaelis-Menten (Km) e catalítica (Kcat), de tripsina para estes substratos de nanoagreagados BSA-Au, foram 1,6×10-5 mol L-1 e 3,8 s-1 a 37 ºC, respectivamente. Este biossensor enzimático é de interesse considerável devido à simplicidade do procedimento, e o método estabelecido tem grande potencial na detecção de outras proteases em diagnósticos clínicos de várias doenças.

A novel, simple, sensitive, and selective fluorometric method was developed for measuring trypsin in biological samples in this article. The method was based upon measuring the quenching of the fluorescence intensity of the bovine serum albumin (BSA) stabilized Au nanoclusters by enzymatic proteolysis. The calibration plot for trypsin was achieved over the concentration range 1-60 nmol L-1 with a correlation coefficient of 0.995 and a limit of detection of 0.6 nmol L-1. The method was also used satisfactorily for the assessment of the trypsin activity and the results showed that the Michaelis-Menten (Km) and catalytic (Kcat) constant values of trypsin for BSA-Au nanoclusters substrate were 1.6×10-5 mol L-1 and 3.8 s-1 at 37 ºC, respectively. This enzyme biosensor is of considerable interest due its promise for simple procedure and the established method has great potential in detection of other proteases in clinical diagnostics of various diseases.

This paper describes a simple, low cost and reliable DNA template preparation protocol for polymerase chain reaction (PCR) using immature leaves from peanut seeds or leaves from field-grown plants. The technique may find wide utility in studies involving PCR-based molecular markers, rapid screening for transformants and gene cloning.

SSRs have proved to be the most powerful tool for variety identification in groundnut of similar origin, and have much potential in genetic and breeding studies. To facilitate SSR discovery in groundnut, we proposed a highly simplified SSR isolation protocol based on multiple enzyme digestion/ligation, mixed biotin-labeled probes and streptavidin coated magnetic beads hybridization capture strategy. Of the 272 colonies randomly picked for sequencing, 119 were found to have unique SSR inserts

Neste trabalho, foi desenvolvido um método para preparação de nanopartículas magnéticas monodispersas funcionalizadas com grupos carboxila. Maguemita de dimensões nanométricas (y-Fe2O3, 7,0 ± 1,0 nm) foi sintetizada usando-se o método de coprecipitação térmica e subseqüentemente coberta com grupos funcionais por copolimerização em suspensão conduzida em uma etapa. Estudos de espectroscopia de infravermelho com transformada de Fourier e análise termogravimétrica confirmaram o sucesso da funcionalização dos grupos carboxila na superfície dos nanocristais magnéticos. Esta superfície química torna possível a purificação de DNA baseada em SPRI (imobilização reversível em fase sólida). Assim, as nanopartículas foram empregadas para isolamento de DNA de cultura de células bacterianas e os resultados demonstraram sua aplicabilidade na preparação de DNA.

In this work, a method was developed to prepare monodispersed carboxyl-group functionalized magnetic nanoparticles. Nanosized maghemite (y-Fe2O3, 7.0 ± 1.0 nm) was synthesized using thermal co-precipitation method and subsequently coated with functional groups by one-step suspension copolymerization. The Fourier transform infrared spectroscopy study and thermogravitmetric analyses confirmed the successful functionalization of carboxyl groups on the surface of magnetic nanocrystals. The surface chemistry makes it possible for SPRI (solid phase reversible immobilization)-based DNA purification. Thus the nanoparticles were employed to isolate plasmid DNA from bacterial cell culture and the results demonstrated its applicability in DNA preparation.