Dynamic allostery in substrate binding by human thymidylate synthase

Human thymidylate synthase (hTS) is essential for DNA replication and therefore a therapeutic target for cancer. Effective targeting requires knowledge of the mechanism(s) of regulation of this 72 kDa homodimeric enzyme. Here, we investigate the mechanism of binding cooperativity of the nucleotide substrate. We have employed exquisitely sensitive methyl-based CPMG and CEST NMR experiments enabling us to identify residues undergoing bifurcated linear 3-state exchange, including concerted switching between active and inactive conformations in the apo enzyme. The inactive state is populated to only ~1.3%, indicating that conformational selection contributes negligibly to the cooperativity. Instead, methyl rotation axis order parameters, determined by 2H transverse relaxation rates, suggest that rigidification of the enzyme upon substrate binding is responsible for the entropically-driven cooperativity. Lack of the rigidification in product binding and substrate binding to an N-terminally truncated enzyme, both non-cooperative, support this idea. In addition, the lack of this rigidification in the N-terminal truncation indicates that interactions between the flexible N-terminus and the rest of the protein, which are perturbed by substrate binding, play a significant role in the cooperativity-a novel mechanism of dynamic allostery. Together, these findings yield a rare depth of insight into the substrate binding cooperativity of an essential enzyme

Analyse au microscope électronique à balayage et au rugosimètre d’impacts laser CO2 sur la dentine

The aim of the study was to compare the morphology of craters produced on the dentinal surface by CO2 laser beams (LASERSATtmCO2) before and after the removal of the carbonized layer, besides with different seetings of the power and duration of the laser beam.Thirty-three recently extracted non carious young third molar teeth were sectionned from vestibular and lingual surfaces, exposing a planed dentinal surface. Twenty impacts were made on each of dentinal surface producing 20 individual craters. The duration and the power of each laser beam were different on each tooth. The duration varied from 0.1 to 0.4 second (0.1 - 0.2 - 0.3 - 0.4 s). The power varied from 1 to 5 watts (1, 2, 3, 4, 5 w).Specimens obtained for a power of 3 and 4 watts and a duration of 0.1 and 0.2 second were examined with a JEOL 35CF (25 KV, magnification: x 30, x 110, x 200), before and after the removal of the carbonized layer. The carbonized layer of the craters was removed with an air polisher (HEATCO).Craters obtained for ail duration values as well as for ail power values were analyzed with a profilometer. The chosen profilometer was: TALISURF 10; horizontal amplification Vh = 20; vertical amplification Vv = 200.Samples were observed by a SEM and the craters depth and diameter were measured with a profilometer. Then, the carbonized layer of the craters was removed with an airpolisher and the cleaned dentinal surface was observed again with the SEM and the profilometer. Measurements were entered in a computer (using the SIPHAR programm) in order to calculate the mean values of the depth, the diameter and the area, for ail test conditions.It appears that the carbonized layer is not adherent to the dentine and can be easily removed. From the mean values, we can conclude that the diameter is about four times larger than the depth for the nocleaned craters and is about five to six times larger than the depth for the cleaned craters. The profils of the craters cannot be used for retention pins in the composite adhesion but the adhesion area is increased after a laser beam.Cette étude a pour but d’observer et de quantifier les cratères produits par un tir focalisé discontinu au laser CO2 (Lasersattm), avant et après élimination de la couche carbonisée par un aéropolisseur. Trentetrois molaires, extraites et indemnes de caries, sont coupées en deux dans le sens mésio-distal et leurs faces vestibulaires et linguales sont sectionnées pour donner une surface dentinaire plane. Vingt cratères sont réalisés par un tir focalisé discontinu sur chaque surface dentinaire. Les temps d’application et les puissances du rayonnement utilisés sont respectivement: 0.1, 0.2, 0.3, 0.4 seconde et 1, 2, 3, 4, 5 watts. Ces cratères sont analysés au microscope électronique à balayage et au rugosimètre, avant et après élimination de la couche carbonisée. Les résultats obtenus sont traités à l’aide du logiciel SIPHAR sur PC; nous obtenons un profil moyen du cratère pour chaque puissance et temps d’application utilisés. Les résultats sont les suivants: le diamètre est environ quatre fois plus grand que la profondeur avant élimination de la couche carbonisée et est cinq à six fois plus important après élimination de cette couche. Le diamètre et la profondeur des cratères sont plus importants après élimination de la couche carbonisée. La couche carbonisée a une épaisseur régulière sauf au fond du cratère où elle est plus faible que sur les parois. Avant élimination de la couche carbonisée le profil du cratère est un cône, après élimination de la couche, le profil est un cône tronqué. En conclusion, les cratères obtenus ne peuvent être considérés comme des ancrages efficaces pour d’éventuels collages dentinaires avec des composites; toutefois la surface d’adhésion s’en trouve considérablement accrue

Medland 2020, une parole partagée sur les forêts méditerranéennes et leurs produits

En proposant, à travers cet article, un regard extérieur sur le projet Medland 2020, l’association Forêt Méditerranéenne s’est prêtée à un exercice difficile, mais ô combien stimulant, puisqu’il touche au cœur de ses réflexions depuis maintenant 35 ans. Chaque expérience présentée dans ce numéro et réalisée dans le cadre de projets de coopération de l’Union européenne, participe à un cadre commun de gestion des territoires méditerranéens en promouvant l’utilisation et la protection des ressources naturelles, la valorisation sociale et économique de ces territoires... Cet article tente d’analyser en quoi la mise en commun et la capitalisation de ces résultats peut apporter un plus aux acteurs de la foresterie méditerranéenne..

Medland 2020, A voice in common for Mediterranean forests and their products

In this article, the association Forêt Méditerranéenne seeks to offer an outsider’s perspective on the Medland 2020 project. A difficult task indeed, but worth every effort because it reaches into the very heart of the association’s preoccupations over the last 35 years. All the experiments and experience presented in this issue took place as part of the European Union’s projects for cooperation, contributing to a shared framework for the management of Mediterranean regions and localities by fostering the use and protection of natural resources and making the most, both economically and socially, out of these territories... This article attempts to analyse how pooling the results and sharing acquired knowhow can boost the success of all those involved in Mediterranean forestry

Risk profiles and one-year outcomes of patients with newly diagnosed atrial fibrillation in India: Insights from the GARFIELD-AF Registry.

BACKGROUND: The Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF) is an ongoing prospective noninterventional registry, which is providing important information on the baseline characteristics, treatment patterns, and 1-year outcomes in patients with newly diagnosed non-valvular atrial fibrillation (NVAF). This report describes data from Indian patients recruited in this registry. METHODS AND RESULTS: A total of 52,014 patients with newly diagnosed AF were enrolled globally; of these, 1388 patients were recruited from 26 sites within India (2012-2016). In India, the mean age was 65.8 years at diagnosis of NVAF. Hypertension was the most prevalent risk factor for AF, present in 68.5% of patients from India and in 76.3% of patients globally (P < 0.001). Diabetes and coronary artery disease (CAD) were prevalent in 36.2% and 28.1% of patients as compared with global prevalence of 22.2% and 21.6%, respectively (P < 0.001 for both). Antiplatelet therapy was the most common antithrombotic treatment in India. With increasing stroke risk, however, patients were more likely to receive oral anticoagulant therapy [mainly vitamin K antagonist (VKA)], but average international normalized ratio (INR) was lower among Indian patients [median INR value 1.6 (interquartile range {IQR}: 1.3-2.3) versus 2.3 (IQR 1.8-2.8) (P < 0.001)]. Compared with other countries, patients from India had markedly higher rates of all-cause mortality [7.68 per 100 person-years (95% confidence interval 6.32-9.35) vs 4.34 (4.16-4.53), P < 0.0001], while rates of stroke/systemic embolism and major bleeding were lower after 1 year of follow-up. CONCLUSION: Compared to previously published registries from India, the GARFIELD-AF registry describes clinical profiles and outcomes in Indian patients with AF of a different etiology. The registry data show that compared to the rest of the world, Indian AF patients are younger in age and have more diabetes and CAD. Patients with a higher stroke risk are more likely to receive anticoagulation therapy with VKA but are underdosed compared with the global average in the GARFIELD-AF. CLINICAL TRIAL REGISTRATION-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01090362

The Brioverian-Pentevrian unconformity revisited in Brittany. Implications for the connection between Anti-Atlas (Morocco) and Armorica

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