RESUMO
Functional DNAs are valuable molecular tools in chemical biology and analytical chemistry but suffer from low activities due to their limited chemical functionalities. Here, we present a chemoenzymatic method for site-specific installation of diverse functional groups on DNA, and showcase the application of this method to enhance the catalytic activity of a DNA catalyst. Through chemoenzymatic introduction of distinct chemical groups, such as hydroxyl, carboxyl, and benzyl, at specific positions, we achieve significant enhancements in the catalytic activity of the RNA-cleaving deoxyribozyme 10-23. A single carboxyl modification results in a 100-fold increase, while dual modifications (carboxyl and benzyl) yield an approximately 700-fold increase in activity when an RNA cleavage reaction is catalyzed on a DNA-RNA chimeric substrate. The resulting dually modified DNA catalyst, CaBn, exhibits a kobs of 3.76 min-1 in the presence of 1 mM Mg2+ and can be employed for fluorescent imaging of intracellular magnesium ions. Molecular dynamics simulations reveal the superior capability of CaBn to recruit magnesium ions to metal-ion-binding site 2 and adopt a catalytically competent conformation. Our work provides a broadly accessible strategy for DNA functionalization with diverse chemical modifications, and CaBn offers a highly active DNA catalyst with immense potential in chemistry and biotechnology.
Assuntos
DNA Catalítico , RNA Catalítico , Sequência de Bases , Magnésio , DNA Catalítico/química , DNA , RNA/química , Íons , Conformação de Ácido Nucleico , Catálise , RNA Catalítico/metabolismoRESUMO
Due to their high accuracy, excellent stability, minor size, and low cost, silicon piezoresistive pressure sensors are used to monitor downhole pressure under high-temperature, high-pressure conditions. However, due to silicon's temperature sensitivity, high and very varied downhole temperatures cause a significant bias in pressure measurement by the pressure sensor. The temperature coefficients differ from manufacturer to manufacturer and even vary from batch to batch within the same manufacturer. To ensure high accuracy and long-term stability for downhole pressure monitoring at high temperatures, this study proposes a temperature compensation method based on bilinear interpolation for piezoresistive pressure sensors under downhole high-temperature and high-pressure environments. A number of calibrations were performed with high-temperature co-calibration equipment to obtain the individual temperature characteristics of each sensor. Through the calibration, it was found that the output of the tested pressure measurement system is positively linear with pressure at the same temperatures and nearly negatively linear with temperature at the same pressures, which serves as the bias correction for the subsequent bilinear interpolation temperature compensation method. Based on this result, after least squares fitting and interpolating, a bilinear interpolation approach was introduced to compensate for temperature-induced pressure bias, which is easier to implement in a microcontroller (MCU). The test results show that the proposed method significantly improves the overall measurement accuracy of the tested sensor from 21.2% F.S. to 0.1% F.S. In addition, it reduces the MCU computational complexity of the compensation model, meeting the high accuracy demand for downhole pressure monitoring at high temperatures and pressures.
RESUMO
Leveraging blackcurrant anthocyanin (BC) as an indicator and carboxymethyl cellulose (CMC), gum xanthan (GX), and citric acid (CA) as film fabricating materials, an innovative amine-responsive beef freshness intelligent film, known as CGC-BC, was successfully created. It was found that the physical characteristics, sensitivity to the biogenic amine reaction, and original color of the film were all highly influenced by the pH of the film-forming solutions. The film's freshness monitoring ability was assessed at 4, 25, and 35 °C, and various color changes were employed to monitor beef deterioration. ΔE values and the visual color difference of the low-concentration (SCG-BC-0.08 and SCG-BC-0.16) ammonia-sensitive indicator films demonstrated significant color changes than the high-concentration (SCG-BC-0.24 and SCG-BC-0.32) films. The films biodegradation (37.16 to 51.49%) ability was enhanced with increase in the proportions of BC. As the TVB-N and pH values of beef increased with the different temperatures and time and different color changes were observed from red to pink, black to brown, and yellow.
RESUMO
Myoglobin (Mb) responsible for meat color is easily oxidized resulting in meat discoloration. Here, betanin red (BR), as a natural pigment and antioxidant, was chosen for enhancing redness and inhibiting oxidation. Multiple spectroscopies, isothermal titration calorimetry and molecular docking demonstrated that BR changed the microenvironment of heme group and amino acid residues of Mb, inhibited the oxidation of oxymyoglobin. The main interaction force was hydrogen bond and one variable binding site provided a continuous protective barrier to realize antioxidation. The combination of antioxidation with the inherent red color of BR offered dual color protection effect on processed beef with the addition amount of 0.2 % BR. BR treatment enhanced the redness by 25.59 â¼ 53.24 % and the sensory acceptance by 4.89 â¼ 14.24 %, and decreased the lipid oxidation by 0.58 â¼ 15.92 %. This study paves a theoretical basis for the application of BR and its structural analogues in meat color protection and other quality improvement.
Assuntos
Mioglobina , Carne Vermelha , Animais , Bovinos , Mioglobina/química , Antioxidantes/metabolismo , Simulação de Acoplamento Molecular , Betacianinas , Carne/análise , Oxirredução , Cor , Carne Vermelha/análiseRESUMO
A survey of various heating strategies, including terminal temperature (70 and 90 °C), step heating (with or without holding at 50 °C for 10 min) and step cooling (with or without holding at 50 °C for 10 min), on the gelation properties of chicken meat paste was conducted. Compared to 70 °C, 90 °C heating drastically increased (p < 0.05) cooking loss (CL) from 5% to > 15% since more immobilized water was pushed out as free water. Step cooling could mitigate the high-temperature-induced CL. The impact of heating strategies on the textural properties of chicken meat is much lower than that on CL. For both 70 °C and 90 °C cooked samples, step heating reduced (p < 0.05) their whiteness by increasing the yellowness. The storage modulus (G') increase during cooling is mainly driven by cooling leaded lower mobility. Overall, low-temperature ramping heating produced excellent meat gel with low energy consumption.
Assuntos
Galinhas , Calefação , Animais , Culinária , Carne , Temperatura , Água , Géis/químicaRESUMO
Repeated freezing and thawing (F-T) happens during long-term storage and transportation due to the temperature variation, causing quality deterioration of beef products and influencing consumer acceptance. This study was aimed to investigate the relationship between quality attributes, protein structural changes and water real-time migration of beef with different F-T cycles. The results showed that multiply F-T cycles damaged the muscle microstructure and protein structure tended to denature and unfold, led lower population of water reabsorbed, thus triggering the decrease of water capacity, especially a decrease of T21 and A21 of completely thawed beef samples, finally affected the quality, such as tenderness, color and lipid oxidation of beef muscle. Beef should not be abused by F-T cycles >3 times, the quality extremely degraded when subjected to 5 or more F-T cycles, and real-time LF-NMR provided a new aspect to help us control the thawing process of beef.
Assuntos
Análise Espectral Raman , Água , Animais , Bovinos , Congelamento , Água/química , Espectroscopia de Ressonância Magnética/métodos , Músculo Esquelético/química , Conformação ProteicaRESUMO
We report a prebiotically relevant solution to the N1-ribosylation of pyrimidine nucleobases, a well-known challenge to the RNA world hypothesis. We found that the presence of metal cations and clay minerals enable the previously unachievable direct ribosylation of uracil. Spectroscopy and chromatography analyses confirmed the formation of ribosylated uracil. The method can be extended to the ribosylation of 2-pyrimidinone. These findings are also compatible with the metal-doped-clay model, developed by our lab for the unified route of the selection of ribose and subsequent syntheses of nucleotide and RNA.
RESUMO
Postmortem changes of sarcoplasmic and myofibrillar protein phosphorylation in pectoralis major (PM) muscle of broilers under pre-slaughter stress were investigated. Broiler chickens were randomly distributed to unstressed control and transport under high environmental temperature groups. PM muscle samples of transport-stressed broilers were classified into normal or pale, soft and exudative (PSE)-like. Sarcoplasmic fraction in PSE-like meat had a higher global phosphorylation level than that in normal meat at the early postmortem stage. The myofibrillar proteins showed diverse phosphorylation patterns at different postmortem times. The stress-induced highly phosphorylated sarcoplasmic proteins were glycometabolic enzymes, which partially contributed to accelerated glycolysis rate. The phosphorylation levels of most sarcomeric proteins identified in the myofibrillar fraction were affected by postmortem time, implying their roles in regulating muscle rigor mortis development. This work contributes to a deeper understanding of the biochemical processes that may lead to stress-induced changes in meat quality.