Multifunctional Microgel-Based Cream Hydrogels for Postoperative Abdominal Adhesion Prevention

Postoperative abdominal adhesions are a common problem after surgery and can produce serious complications. Current antiadhesive strategies focus mostly on physical barriers and are unsatisfactory and inefficient. In this study, we designed and synthesized advanced injectable cream-like hydrogels with multiple functionalities, including rapid gelation, self-healing, antioxidation, anti-inflammation, and anti-cell adhesion. The multifunctional hydrogels were facilely formed by the conjugation reaction of epigallocatechin-3-gallate (EGCG) and hyaluronic acid (HA)-based microgels and poly(vinyl alcohol) (PVA) based on the dynamic boronic ester bond. The physicochemical properties of the hydrogels including antioxidative and anti-inflammatory activities were systematically characterized. A mouse cecum-abdominal wall adhesion model was implemented to investigate the efficacy of our microgel-based hydrogels in preventing postoperative abdominal adhesions. The hydrogels, with a high molecular weight HA, significantly decreased the inflammation, oxidative stress, and fibrosis and reduced the abdominal adhesion formation, compared to the commercial Seprafilm group or Injury-only group. Label-free quantitative proteomics analysis demonstrated that S100A8 and S100A9 expressions were associated with adhesion formation; the microgel-containing hydrogels inhibited these expressions. The microgel-containing hydrogels with multifunctionality decreased the formation of postoperative intra-abdominal adhesions in a murine model, demonstrating promise for clinical applications.

Structural and physico-chemical characterization of a dirhamnolipid biosurfactant purified from Pseudomonas aeruginosa: application of crude biosurfactant in enhanced oil recovery

The present study describes the structural characterization and biotechnological application of a dirhamnolipid biosurfactant produced byPseudomonas aeruginosastrain NBTU-01 isolated from a petroleum oil-contaminated soil sample.

Identification and characterization of a hitherto unknown nucleotide-binding domain and an intricate interdomain regulation in HflX-a ribosome binding GTPase

A role for HflX in 50S-biogenesis was suggested based on its similarity to other GTPases involved in this process. It possesses a G-domain, flanked by uncharacterized N- and C-terminal domains. Intriguingly, Escherichia coli HflX was shown to hydrolyze both GTP and adenosine triphosphate (ATP), and it was unclear whether G-domain alone would explain ATP hydrolysis too. Here, based on structural bioinformatics analysis, we suspected the possible existence of an additional nucleotide-binding domain (ND1) at the N-terminus. Biochemical studies affirm that this domain is capable of hydrolyzing ATP and GTP. Surprisingly, not only ND1 but also the G-domain (ND2) can hydrolyze GTP and ATP too. Further; we recognize that ND1 and ND2 influence each other’s hydrolysis activities via two salt bridges, i.e. E29-R257 and Q28-N207. It appears that the salt bridges are important in clamping the two NTPase domains together; disrupting these unfastens ND1 and ND2 and invokes domain movements. Kinetic studies suggest an important but complex regulation of the hydrolysis activities of ND1 and ND2. Overall, we identify, two separate nucleotide-binding domains possessing both ATP and GTP hydrolysis activities, coupled with an intricate inter-domain regulation for Escherichia coli HflX.

Exploring potassium-dependent GTP hydrolysis in TEES family GTPases

GTPases are important regulatory proteins that hydrolyze GTP to GDP. A novel GTP-hydrolysis mechanism is employed by MnmE, YqeH and FeoB, where a potassium ion plays a role analogous to the Arginine finger of the Ras-RasGAP system, to accelerate otherwise slow GTP hydrolysis rates. In these proteins, two conserved asparagines and a ‘K-loop’ present in switch-I, were suggested as attributes of GTPases employing a K⁺-mediated mechanism. Based on their conservation, a similar mechanism was suggested for TEES family GTPases. Recently, in Dynamin, Fzo1 and RbgA, which also conserve these attributes, a similar mechanism was shown to be operative. Here, we probe K⁺-activated GTP hydrolysis in TEES (TrmE-Era-EngA-YihA-Septin) GTPases – Era, EngB and the two contiguous G-domains, GD1 and GD2 of YphC (EngA homologue) – and also in HflX, another GTPase that also conserves the same attributes. While GD1-YphC and Era exhibit a K⁺-mediated activation of GTP hydrolysis, surprisingly GD2-YphC, EngB and HflX do not. Therefore, the attributes identified thus far, do not necessarily predict a K⁺-mechanism in GTPases and hence warrant extensive structural investigations.