Combined docking and molecular dynamics simulations to enlighten the capacity of Pseudomonas cepacia and Candida antarctica lipases to catalyze quercetin acetylation

A combined docking and molecular dynamics protocol was applied to investigate quercetin binding modes within the catalytic cavity of Candida antarctica lipase B (CALB) and Pseudomonas cepacia lipase (PCL), aiming to explain the difference of specificity of these enzymes in acetylation reaction. For both lipases, docking of quercetin yielded two families of conformers with either the quercetin A or B-ring pointing towards the catalytic residues. Molecular dynamics (MD) calculations were subsequently performed on several complexes of each family. MD trajectories were analyzed focusing on the orientation of the acyl donor bound to the catalytic serine towards the oxyanion hole residues and the proximity of quercetin hydroxyl groups to the catalytic residues. Results showed that with CALB, the acetate was not correctly positioned within the oxyanion hole whatever the orientation of quercetin, suggesting that no product could be obtained. With PCL, the acetate remained within the oxyanion hole during all MD trajectories. Depending on quercetin orientation, either the 7-OH group or the 3, 5, 3′, 4′-OH groups came alternatively near the catalytic residues, suggesting that all of them could be acylated. The capacity of models to explain the regioselectivity of the reaction was discussed. Key residues and interactions involved in quercetin binding modes were identified and related to the reaction feasibility.     

Efficacy of Photobiomodulation and Metformin on Diabetic Cell Line of Human Periodontal Ligament Stem Cells through Keap1/Nrf2/Ho-1 Pathway

Background:Diabetes mellitus (DM) is a metabolic disorder resulting from hyperglycemia. Hyperglycemia contributes to oxidative stress, and the release of advanced glycation end products (AGEs) further promotes disease pathogenesis. Uncontrolled diabetes reflects great oral complications and affects human oral health. So, the present study aimed to assess the effects of photobiomodulation therapy (PBMT) and Metformin on proliferation and viability of human periodontal ligament stem cells (HPDLSCs) cultured in high glucose medium.Methods:HPDLSCs were collected, isolated, and characterized and then divided into eight groups. Addition of extra glucose to diabetic groups 24 hours before cell irradiations. Metformin was added to half of the diabetic groups. Cells were irradiated with 808 nm diode laser 24, 48 hours. Cell viability was analyzed with MTT assay 24 hours post-irradiation to detect cell viability in each group. Real-time (PCR) was used to evaluate gene expression of Nrf2, Keap1, PIK3, and HO-1 and the effect of PBMT on Keap1/Nrf2/Ho-1 Pathway. ELISA reader was used to evaluating cell viability through (ROS, TNF-α, IL-10) protein levels after cell irradiation.Results:Photobiomodulation at 1, 2, and 3 J/cm2 combined with metformin significantly promoted diabetic cell lines of HPDLSCs viability (in MTT assay and ELISA reader of ROS, TNF-α, IL-10 results) and gene expression of Nrf2, Keap1, PIK3, and HO-1 levels (p< 0.05).Conclusion:photobiomodulation with 3 J/cm² combined with metformin enhanced proliferation and viability of diabetic cell lines of HPDLSCs and thus could improve differentiation and function of diabetic cell lines of HPDLSCs with minimum side effects.Key Words: Diabetes Mellitus, Metformin, Periodontal Ligament Stem Cells, Photobiomodulation     

Cryopreservation of ex-vitro-grown Rosa chinensis ‘Old Blush’ buds using droplet-vitrification and encapsulation-dehydration

Axillary buds from greenhouse-grown plants of Rosa chinensis ‘Old Blush’ were successfully used to establish cryopreservation protocols using both droplet-vitrification and encapsulation-dehydration methods. In droplet vitrification, regrowth occurred after exposure to liquid nitrogen even without pre-culture in the loading solution (LS) before immersion in the plant vitrification solution 2 (PVS2). However, a 20–80 min LS step followed by a short immersion in PVS2 for 3 or 15 min, at 0 °C gave the best regrowth rates (82–86 %). In encapsulation dehydration, the level of dehydration significantly influenced shoot regrowth. The best regrowth rate, 60 %, was obtained at a bead water content of 0.35 g water per g dry weight. These results demonstrate the possibility of using greenhouse plants of rose for cryopreservation by droplet vitrification and encapsulation dehydration.     

FrzS acts as a polar beacon to recruit SgmX,a central activator of type IV pili during Myxococcus xanthus motility

In rod‐shaped bacteria, type IV pili (Tfp) promote twitching motility by assembling and retracting at the cell pole. In Myxococcus xanthus, a bacterium that moves in highly coordinated cell groups, Tfp are activated by a polar activator protein, SgmX. However, while it is known that the Ras‐like protein MglA is required for unipolar targeting, how SgmX accesses the cell pole to activate Tfp is unknown. Here, we demonstrate that a polar beacon protein, FrzS, recruits SgmX at the cell pole. We identified two main functional domains, including a Tfp‐activating domain and a polar‐binding domain. Within the latter, we show that the direct binding of MglA‐GTP unveils a hidden motif that binds directly to the FrzS N‐terminal response regulator (CheY). Structural analyses reveal that this binding occurs through a novel binding interface for response regulator domains. In conclusion, the findings unveil the protein interaction network leading to the spatial activation of Tfp at the cell pole. This tripartite system is at the root of complex collective behaviours in this predatory bacterium.     

Ecdysteroid Titres and Cuticle Depositions in Embryos of the Dipteran Calliphora erythrocephala

Summary

Before the shortening of the germ band, embryos of Calliphora erythrocephala secrete an electron dense layer which resembles a thin atypical cuticle. After completion of the dorsal closure, a second, typical, cuticle is deposited. It is characterized by a thick procuticle and by the presence of hooked setae. This cuticle develops into the larval cuticle of the first instar.

We did not find in newly-laid eggs of Calliphora detectable amounts of either free or hydrolysable conjugated ecdysteroids. A marked rise in ecdysteroid concentrations, essentially attributable to free ecdysone and 20- hydroxyecdysone, occurs shortly before the deposition of the typical cuticle. After a transient decrease, the ecdysteroid titre rises again before hatching.

When eggs are mid-ligatured at blastula or early gastrula stages, the posterior embryonic half is able to build up a typical cuticle with hooked setae. This cuticulogenesis is therefore not dependent on the presence of the embryonic ring glands.     

Phosphorylation controls the interaction of the connexin43 C-terminal domain with tubulin and microtubules

Connexins are structurally related transmembrane proteins that assemble to form gap junction channels involved in the mediation of intercellular communication. It has been shown that the intracellular tail of connexin43 (Cx43) interacts with tubulin and microtubules with putative impacts on its own intracellular trafficking, its activity in channel communication, and its interference with specific growth factor signal transduction cascades. We demonstrate here that the microtubule binding of Cx43 is mainly driven by a short region of 26 amino acid residues located within the intracellular tail of Cx43. The nuclear magnetic resonance structural analysis of a peptide (K26D) corresponding to this region shows that this peptide is unstructured when free in solution and adopts a helix conformation upon binding with tubulin. In addition, the resulting K26D-tubulin molecular complex defines a new structural organization that could be shared by other microtubule partners. Interestingly, the K26D-tubulin interaction is prevented by the phosphorylation of K26D at a src kinase specific site. Altogether, the results elucidate the mechanism of the interaction of Cx43 with the microtubule cytoskeleton and propose a pathway for understanding the microtubule-dependent regulation of Cx43 gap junctional communications and the involvement of Cx43 in TGF-β signal transduction.     

Physiological and structural modifications induced by cadmium-calcium interaction in tomato (Lycopersicon esculentum)

Tomato seedlings (Lycopersicon esculentum), initially cultivated in a basic nutrient solution during 12 days, were treated with increasing CdCl(2) concentrations for 10 days. The results showed that cadmium inhibited the weight growth depending on the metal concentration and the plant organ. In the presence of 20 microM CdCl(2), the addition of calcium, 0.1 to 10 mM of CaCl(2) in the culture medium, improved especially the biomass production and the mineral composition of the plants in concomitance with an increase in the contents of photosynthetic pigments. Histological study at the hypocotyle level revealed that cadmium (20 microM) induced a restriction of the tissue territories as well as meristem formations differentiating in a root structure. At this concentration, the addition of CaCl(2) (5 microM) was characterized by an opposite effect with absence of meristem structures. The overall results suggest that the alteration of some plant growth process after exposure to cadmium can be attenuated by an adequate calcium contribution in culture medium.