How does chiral self-sorting take place in the formation of homochiral Pd₆L₈ capsules consisting of cyclotriveratrylene-based chiral tritopic ligands?

The chiral self-sorting process during the self-assembly of homochiral Pd6L8 capsules from cyclotriveratrylene (CTV)-based chiral tritopic ligands (L) and Image ID:c8sc01062e-t1.gif (Py*: 3-chloropyridine) was investigated by an NMR-based approach (QASAP: quantitative analysis of the self-assembly process). From the beginning to the formation of the Image ID:c8sc01062e-t2.gif immature capsules (ICs), enantiomeric ligands are distributed in the intermediates in a non-self-sorting manner, which leads to the isomers of heterochiral ICs over 99% yield. The mismatch of the chirality in the heterochiral ICs prevents intramolecular ligand exchanges in ICs to form the heterochiral capsules. The correction of the chirality in the heterochiral ICs (chiral self-sorting) takes place very slowly to finally lead to the homochiral capsules. The reason why the chiral self-sorting took place in the late stage of the self-assembly (after the formation of the heterochiral ICs) would be due to the relatively high flexibility of the CTV-based ligand

From Coagulation to Oral Surgery Application: Platelets in Bone Regeneration

International audienceThe complexity of the treatment of tissue lesions, particularly bone lesions, in regenerative medicine depends on the origin of the substance loss (traumatic, tumoral, infectious, etc.), its size and mechanical requirements. In the field of dental surgery, the need to ensure rapid regeneration of injured bone tissue for periodontal, post-extractional or pre-implant corrective surgery leads dental surgeons to have a large number of biomaterials in their therapeutic arsenal. The mineral materials are most often used because of their chemical composition which is close to bone’s mineral phase. They also present a resorption time in agreement with the time of formation of new bone.However their benefits are inconstant and the need of new bioactive structures, well accepted by the host, and favoring tissue healing has grown. Here is the place for platelet concentrates such as Platelet Rich Plasma (PRP) and Platelet Rich Fibrin (PRF) which are rich in growth factors, cytokines and others proteins. PRF became the most commonly used in the last decade as it is easier to handle with its polymerized form which mimics an extracellular matrix favorable to cell proliferation and differentiation. A new option, called platelet lysate, has recently been highlighted in the general field of tissue regeneration and has the advantage of making platelet’s content directly available. Proteins concentrations are increased in these products even if their liquid form complicates their use in daily practice. This mini-review sums up the main clinical interests for the use of platelet concentrates and the new perspectives in the field of alveolar bone regeneration especially with platelet lysate

Oral care of a patient with a SAPHO syndrome and a nickel allergy

SAPHO is an acronym for Synovitis, Acne, Pustulosis, Hyperostosis and Osteitis. The syndrome is difficult to diagnose because it may present many different manifestations in adults and children. Its origin is still unknown, although some infectious, genetic and immune hypotheses have been put forward. We report the case of a 49‐year‐old woman with SAPHO syndrome, who developed a serious cutaneous allergy following the insertion of a removable partial denture (RPD). The oral care and treatment of this patient are described

Involvement of DnaE, the second replicative DNA polymerase from Bacillus subtilis, in DNA mutagenesis

In a large group of organisms including low G + C bacteria and eukaryotic cells, DNA synthesis at the replication fork strictly requires two distinct replicative DNA polymerases. These are designated pol C and DnaE in Bacillus subtilis. We recently proposed that DnaE might be preferentially involved in lagging strand synthesis, whereas pol C would mainly carry out leading strand synthesis. The biochemical analysis of DnaE reported here is consistent with its postulated function, as it is a highly potent enzyme, replicating as fast as 240 nucleotides/s, and stalling for more than 30 s when encountering annealed 5'-DNA end. DnaE is devoid of 3' --> 5'-proofreading exonuclease activity and has a low processivity (1-75 nucleotides), suggesting that it requires additional factors to fulfill its role in replication. Interestingly, we found that (i) DnaE is SOS-inducible; (ii) variation in DnaE or pol C concentration has no effect on spontaneous mutagenesis; (iii) depletion of pol C or DnaE prevents UV-induced mutagenesis; and (iv) purified DnaE has a rather relaxed active site as it can bypass lesions that generally block other replicative polymerases. These results suggest that DnaE and possibly pol C have a function in DNA repair/mutagenesis, in addition to their role in DNA replication

From Coagulation to Oral Surgery Application: Platelets in Bone Regeneration

The complexity of the treatment of tissue lesions, particularly bone lesions, in regenerative medicine depends on the origin of the substance loss (traumatic, tumoral, infectious, etc.), its size and mechanical requirements. In the field of dental surgery, the need to ensure rapid regeneration of injured bone tissue for periodontal, post-extractional or pre-implant corrective surgery leads dental surgeons to have a large number of biomaterials in their therapeutic arsenal. The mineral materials are most often used because of their chemical composition which is close to bone’s mineral phase. They also present a resorption time in agreement with the time of formation of new bone.However their benefits are inconstant and the need of new bioactive structures, well accepted by the host, and favoring tissue healing has grown. Here is the place for platelet concentrates such as Platelet Rich Plasma (PRP) and Platelet Rich Fibrin (PRF) which are rich in growth factors, cytokines and others proteins. PRF became the most commonly used in the last decade as it is easier to handle with its polymerized form which mimics an extracellular matrix favorable to cell proliferation and differentiation. A new option, called platelet lysate, has recently been highlighted in the general field of tissue regeneration and has the advantage of making platelet’s content directly available. Proteins concentrations are increased in these products even if their liquid form complicates their use in daily practice. This mini-review sums up the main clinical interests for the use of platelet concentrates and the new perspectives in the field of alveolar bone regeneration especially with platelet lysate

Thermogravimetric study of the behaviour of organic and inorganic polymers contained in four dental resin-based composites

The composition of dental resin-based composite (RBC) matrix is partly responsible for many clinical failures in restorations, which may come from dimensional variation or instability in a wet environment. The objective of this study is therefore to evaluate the thermal stability over time of four dental RBC with different matrices. Silicone cylinders were filled with four different materials and then photopolymerized. To simulate ageing in the buccal environment, half of the samples were placed in a dark place at 37°C for 45 days in sealed compartments containing 2 ml of water. All the RBC produced were subjected to thermogravimetric analysis to measure the loss of mass as a function of temperature. Bis-GMA-based resins and Ormocer materials have similar curves before and after soaking in humid atmosphere. The curves of the UDMA resin are different before and after water ageing, meaning that water imbibition has modified the structure of the composite and its degradation. Even if many curves are similar within the same RBC at different polymerization times or at different pre- and post-ageing times, it is rare to observe a common kinetics between two different composites. Our results show good wet stability of polymerized dental RBC according to the manufacturer’s instructions, although the UDMA-based materials show more variation. It therefore seems that Ormocer resin composite with mass placement have ageing properties that can compete with those of conventional composites whereas those incremented on 2 mm layers are more sensitive to the time necessary for polymerization

Bioceramic powders for bone regeneration modified by high-pressure CO2 process

Non-stoichiometric nanocrystalline apatites present enhanced bioactivity compared to stoichiometric hydroxyapatite. The purpose of this work was to modify the calcium phosphates (CaP) generally used to prepare bioactive ceramics in the aim of obtaining a biomimetic apatite powder. Hydroxyapatite (HA) powder, amorphous tricalcium phosphate (amTCP) powder and a blend of these two were modified by means of an innovative, simple, “green” carbonation process, involving water and high-pressure CO2 (80 bar). This process induced a modification of the CaP, which is sensitive to the environment in which it is located and, in particular, to the pH variations that occur during the treatment phase (decrease in the pH) and during the degassing phase (return to neutral pH). FTIR and Raman spectroscopy, XRD and SEM analyses showed that, depending on the type of initial CaP powder, high-pressure CO2 treatment led to the formation of different types of calcium phosphate phases. This process allowed partial dissolution of the initial powder, mainly of TCP when present, and precipitation of a new CaP phase. HA and HA/amTCP powders were transformed into a mixture of OCP and immature carbonated apatite (PCCA) phases, including OCP maturation/transformation into PCCA. In the case of amTCP powder, a DCPD phase was also present due to the high TCP solubility and an earlier precipitation during the degassing step. This work shows the great potential of such an innovative low-temperature and high-pressure process to transform HA, HA/TCP and TCP powder into bioactive biphasic ceramics composed of OCP and PCCA similar to bone mineral

Genetic Evidence for a Link Between Glycolysis and DNA Replication

BACKGROUND: A challenging goal in biology is to understand how the principal cellular functions are integrated so that cells achieve viability and optimal fitness in a wide range of nutritional conditions. METHODOLOGY/PRINCIPAL FINDINGS: We report here a tight link between glycolysis and DNA synthesis. The link, discovered during an analysis of suppressors of thermosensitive replication mutants in bacterium Bacillus subtilis, is very strong as some metabolic alterations fully restore viability to replication mutants in which a lethal arrest of DNA synthesis otherwise occurs at a high, restrictive, temperature. Full restoration of viability by such alterations was limited to cells with mutations in three elongation factors (the lagging strand DnaE polymerase, the primase and the helicase) out of a large set of thermosensitive mutants affected in most of the replication proteins. Restoration of viability resulted, at least in part, from maintenance of replication protein activity at high temperature. Physiological studies suggested that this restoration depended on the activity of the three-carbon part of the glycolysis/gluconeogenesis pathway and occurred in both glycolytic and gluconeogenic regimens. Restoration took place abruptly over a narrow range of expression of genes in the three-carbon part of glycolysis. However, the absolute value of this range varied greatly with the allele in question. Finally, restoration of cell viability did not appear to be the result of a decrease in growth rate or an induction of major stress responses. CONCLUSIONS/SIGNIFICANCE: Our findings provide the first evidence for a genetic system that connects DNA chain elongation to glycolysis. Its role may be to modulate some aspect of DNA synthesis in response to the energy provided by the environment and the underlying mechanism is discussed. It is proposed that related systems are ubiquitous

Attempted Resolution and Racemization of Beckmann‐Derived CTV‐Lactam and the Use of Chirabite‐AR® to Determine the Optical Purity of the Supramolecular Scaffold

Chirabite‐AR was employed to differentiate enantiomers of the axially chiral cyclotriveratrylene (CTV)‐derived macrocyclic lactam with baseline separation of most of the proton NMR resonances enabling enantiomeric purity determination of this supramolecular scaffold. Attachment of menthyloxy acetic acid as a chiral auxiliary to the CTV‐Beckmann derived lactam afforded diastereomers that were enriched to a ratio of 87:13, as confirmed by both 1H NMR and single‐crystal X‐ray diffraction. Basic hydrolysis of the enriched diastereomeric mixture proceeded with rapid bowl inversion to yield racemic CTV‐lactam as confirmed by Chirabite‐AR NMR analysis. Density functional theory (DFT) calculations (M06 2X/6‐31G*) were performed on the crown and saddle conformers of the CTV‐lactam

Misdiagnosed Tooth Aspiration in a Young Handicapped Boy: Case Report and Recommendations

Tooth inhalation remains a rare incident but it may occur during dental care, especially in children. We report here the case of a four-year-old boy with Down syndrome who came to the hospital after a dental trauma. During the extraction procedure, he aspired his maxillary incisor without presenting any signs of respiratory distress and was discharged by the surgical team, who thought that he had swallowed the tooth. Three weeks later, he was admitted to the emergency service because of a pulmonary infection. Two endoscopy interventions under general anesthesia were necessary to recover the foreign body inside the left lung. Because of the multiple symptoms associated with the trisomy 21 syndrome (general hypotonia, impaired immunity, etc.), practitioners should be very mindful of aspiration risks and complications during dental care. The systematic prescription of lung radiography would prevent the onset of pulmonary infections and enable an earlier intervention