No abstract

Water plays an indispensable role in the gelation of proteins, but its function still remains unclear. In this work, the variation of water species with the structural changes of globular proteins was investigated using temperature-dependent near infrared (NIR) spectroscopy. Ovalbumin (OVA) was used as a model protein, which forms a gel-like structure as the temperature increases through three phases, i.e., phase I (native), phase II (molten globule state), and phase III (gel state). The structural change and the content variation of different water species in the three phases of gelation were analyzed by two-dimensional correlation NIR spectroscopy and Gaussian fitting. A decrease in the water species with two hydrogen bonds (S2) was found and the change follows the same phases as OVA. In the first two phases, the change occurs after those of other water species but in the third phase, the change is faster than that of free water species. The result indicates that in the native and molten globule states, S2 is located in the hydration shell of OVA to maintain the stability of the protein structure, and then in the gel state, high temperature weakens the hydrogen bonding of S2 and leads to the destruction of the hydration shell, making OVA clusters form a gel structure.

Rapid start-up of partial nitrification is of great significance for subsequent denitrification and the anammox process; however, slow nitritation hinders the application of these processes. The current study presents a novel strategy for achieving nitritation using aerobic starvation and controlling sludge retention time (SRT). Activated sludge with a high level of complete nitrification was introduced into an aerated reactor without feeding to start the aerobic starvation. The results showed that nitritation was rapidly achieved, while the shorter SRT (15 days) guaranteed the stability of nitritation with an average nitrite accumulation ratio (NAR) of more than 95%. The activity recovery rates of ammonium-oxidizing bacteria (AOB; from 0.20 ± 0.00 d to 0.29 ± 0.08 d) were higher than those of nitrite-oxidizing bacteria (NOB; -0.11 ± 0.02 d to 0.16 ± 0.05 d) during the reactivation periods. Furthermore, the transcriptional responses of amoA and hao mRNA after aerobic starvation were faster than that of the nxrB gene, which explained the fast occurrence of nitritation after the aerobic starvation period. The quantitative real-time PCR (qPCR) analysis showed that the cell number of nitrifying bacteria remained stable during the starvation process, whereas the AOB population gradually became dominant over that of NOB in the reactivation period. These observations strongly supported the feasibility of accelerating the establishment of nitritation using aerobic starvation.

No abstract

No abstract

No abstract

Hydrogen cyanide is a well-known toxic component in cigarette smoke. Accurate determination of hydrogen cyanide is of great significance to assess the risk of cigarettes to public health.

ARHT is a new subgroup of the Rho family identified recently, which consists of two Rho-like genes, Arht1 and Arht2. ARHT may be involved in mitochondrial homeostasis and apoptosis. Constitutively active mutants of ARHT1 induced an aggregation of the mitochondrial network and resulted in an increased apoptotic rate of the cells. Here we report the molecular cloning and characterization of a novel mouse cDNA encoding a putative atypical GTPase protein, Arht2. Mouse Arht2 consists of 19 exons and has been mapped to mouse chromosome 17A3.3. Both human and mouse Arht2 genes are ubiquitously expressed in adult tissues. The results of RT-PCR experiments indicated that the Arht2 gene is expressed in all stages of mouse testis and reached the adult level of transcription at postnatal day 30. In situ hybridization revealed strong hybridization signals of Arht2 in residual bodies. In the mouse testis, Arht2 may be involved in the differentiation of testis and spermiogenesis. The molecular characterization of the mouse Arht2 gene may provide a clue for functional studies of the human ARHT genes.