Elucidating the protein cold-adaptation: Investigation of the parameters enhancing protein psychrophilicity

To investigate the role of the critical parameters in adaptation of proteins to low temperatures, a comparative systematic analysis was performed. Several parameters were proposed to have contribution to cold adaptation of proteins. Among proposed parameters, total values of residual structure states, secondary structure states and oligomeric states were alike in both psychrophilic and mesophilic proteins. In addition, our results provided new quantitative information about the trends in the substitution preference of Ile, Phe, Tyr, Lys, Arg, His, Glu and Leu with most of amino acids and substitution avoidance of Gly, Thr and Ala with most of amino acids. These findings would help future efforts propose a strategy for designing psychrophilic proteins.     

Microencapsulation of Bacteriophage Felix O1 into Chitosan-Alginate Microspheres for Oral Delivery

This paper reports the development of microencapsulated bacteriophage Felix O1 for oral delivery using a chitosan-alginate-CaCl₂ system. In vitro studies were used to determine the effects of simulated gastric fluid (SGF) and bile salts on the viability of free and encapsulated phage. Free phage Felix O1 was found to be extremely sensitive to acidic environments and was not detectable after a 5-min exposure to pHs below 3.7. In contrast, the number of microencapsulated phage decreased by 0.67 log units only, even at pH 2.4, for the same period of incubation. The viable count of microencapsulated phage decreased only 2.58 log units during a 1-h exposure to SGF with pepsin at pH 2.4. After 3 h of incubation in 1 and 2% bile solutions, the free phage count decreased by 1.29 and 1.67 log units, respectively, while the viability of encapsulated phage was fully maintained. Encapsulated phage was completely released from the microspheres upon exposure to simulated intestinal fluid (pH 6.8) within 6 h. The encapsulated phage in wet microspheres retained full viability when stored at 4°C for the duration of the testing period (6 weeks). With the use of trehalose as a stabilizing agent, the microencapsulated phage in dried form had a 12.6% survival rate after storage for 6 weeks. The current encapsulation technique enables a large proportion of bacteriophage Felix O1 to remain bioactive in a simulated gastrointestinal tract environment, which indicates that these microspheres may facilitate delivery of therapeutic phage to the gut.     

Activity of the Bcr GTPase-activating domain is regulated through direct protein/protein interaction with the Rho guanine nucleotide dissociation inhibitor

The cycling of Rac GTPases, alternating between an active GTP- and an inactive GDP-bound state, is controlled by guanine nucleotide exchange factors, GTPase-activating proteins (GAPs), and guanine nucleotide dissociation inhibitors (GDIs). Little is known about how these controlling activities are coordinated. Studies using null mutant mice have demonstrated that Bcr and Abr are two physiologically important GAPs for Rac. Here, we report that in the presence of RhoGDIalpha, Bcr is unable to convert Rac-GTP to Rac-GDP because RhoGDI forms a direct protein complex with Bcr. Interestingly, RhoGDIalpha binds to the GAP domain in Bcr and Abr, a domain that also binds to Rac-GTP and catalyzes conversion of the bound GTP to GDP on Rac. The presence of activated Rac diminished the Bcr/RhoGDIalpha interaction. Moreover, a Bcr mutant that lacks the ability to promote hydrolysis of Rac-GTP bound to its GAP domain did not bind to RhoGDIalpha in cell lysates, indicating that binding of RhoGDIalpha and Rac-GTP to the Bcr GAP domain is mutually exclusive. Our results provide the first identification of a protein that regulates BcrGAP activity.     

Upper Maastrichtian depositional environments and sea-level history of the Kopet-Dagh Intracontinental Basin, Kalat Formation, NE Iran

The Kopet-Dagh Basin is located in northeastern Iran and southern Turkmenistan. The Late Maastrichtian Kalat Formation caps the Cretaceous interval in this Basin. Based on eight measured stratigraphic sections, the depositional environments and the sea-level history of the Kalat Formation have been interpreted. Petrographic and field observations led to identification of four major carbonates (A–D) and two siliciclastic lithofacies types. Carbonate rocks were deposited on a ramp setting within three zones including restricted and semi-restricted lagoons, bars, and open marine environments, while the siliciclastics were deposited at the shoreline. Sequence stratigraphic analysis identified two depositional sequences in the western and eastern parts and three depositional sequences in the central parts of the study area. Comparing the sea-level curve of Late Maastrichtian time in the Kopet-Dagh Basin with the global sea-level curve for the same time interval, there are some geometrical similarities and differences. The variations in the Basin are related to regional tectonic settings and sediment loading of the study area. Reconstructions of depositional environment during eight time slices of the Late Maastrichtian are presented. These results could be used for comparison with other localities worldwide and provide additional data for Late Cretaceous paleogeographic reconstructions.     

Design,construction, and optimization of a novel,modular, and scalable incubation chamber for continuous viral inactivation

We designed, built or 3D printed, and screened tubular reactors that minimize axial dispersion to serve as incubation chambers for continuous virus inactivation of biological products. Empirical residence time distribution data were used to derive each tubular design's volume equivalent to a theoretical plate (VETP) values at a various process flow rates. One design, the Jig in a Box (JIB), yielded the lowest VETP, indicating optimal radial mixing and minimal axial dispersion. A minimum residence time (MRT) approach was employed, where the MRT is the minimum time the product spends in the tubular reactor. This incubation time is typically 60 minutes in a batch process. We provide recommendations for combinations of flow rates and device dimensions for operation of the JIB connected in series that will meet a 60‐min MRT. The results show that under a wide range of flow rates and corresponding volumes, it takes 75 ± 3 min for 99% of the product to exit the reactor while meeting the 60‐min MRT criterion and fulfilling the constraint of keeping a differential pressure drop under 5 psi. Under these conditions, the VETP increases slightly from 3 to 5 mL though the number of theoretical plates stays constant at about 1326 ± 88. We also demonstrated that the final design volume was only 6% ± 1% larger than the ideal plug flow volume. Using such a device would enable continuous viral inactivation in a truly continuous process or in the effluent of a batch chromatography column. Viral inactivation studies would be required to validate such a design. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:954–965, 2017     

Influence of Meloidogyne hapla Chitwood, 1949 on Development and Establishment of Heterodera schachtii Schmidt, 1871 on Beta vulgaris L

Influence of Meloidogyne hapla on estahlishnrent and maturity of Heterodera schachtii in sugarbeet was studied. Results indicated that when the majority of M. hapla were in second, third, or fourth larval stages within plants prior to H. schachtii inoculation, growth and development of the latter was retarded. However, when M. hapla reached the young female stage prior to inoculation of H. schachtii, establishment and development of the latter was greatly enhanced. As M. hapla reached maturity before and after egg production prior to H. schachtii inoculation, establishment and growth of the latter was progressively decreased. In each instance, M. hapla developed independently and matured at the same rate as in plants inoculated with only M. hapla. Usually ratios of total soluble carbohydrates to reducing carbohydrates were lower, but not significantly different, in plants receiving both nematodes as compared to other treatments.