How the folding rate constant of simple, single-domain proteins depends on the number of native contacts

Experiments have shown that the folding rate constants of two dozen structurally unrelated, small, single-domain proteins can be expressed in terms of one quantity (the contact order) that depends exclusively on the topology of the folded state. Such dependence is unique in chemical kinetics. Here we investigate its physical origin and derive the approximate formula ln(k) = ln(N) + a + bN, were N is the number of contacts in the folded state, and a and b are constants whose physical meaning is understood. This formula fits well the experimentally determined folding rate constants of the 24 proteins, with single values for a and b.     

Choroidal neovascularization---physiopathologic theories

The Age-Related Macular Degeneration is an extremely serious health problem for the elderly people. The therapeutic options are not so effective, but there are a plenty of physiopathologic theories and hypothesis for logical epidemiology and etiology. We are looking through this theoretical aspects and try to identify what is necessary for clinical practice.     

Intraoperative hemofiltration in adults: prevention of hypercirculatory syndrome?

Hypercirculatory syndrome (HCS) after cardiac surgery may be a sequela of extracorporeal circulation due to hemodilution and release of inflammatory mediators. The aim of this study was to investigate the influence of intraoperative hemofiltration (HF) on the incidence of HCS. A prospective cohort study of 80 patients scheduled for elective coronary bypass was performed. The patients were randomized to two groups: in the conventional (CONV) group 40 patients were treated conventionally and in the HF group 40 patients underwent intraoperative HF. There was no perioperative mortality. The incidence of HCS was comparable in both groups (32% in CONV group versus 40% in HF group; n.s.). Mean cardiac output was higher and systemic vascular resistance lower in CONV group patients than in HF group patients, however these differences did not reach statistical significance. According to this data intraoperative HF does not prevent postoperative HCS induced by cardiopulmonary bypass. Further studies are required to identify the etiology of HCS, and to prevent it occurring after open-heart surgery.     

Eineiige Zwillinge mit progressiver Muskeldystrophie

Summary The observation of a couple of concordant monozygotic twins with X-recessive progressive muscular dystrophy of Duchenne's type is presented. Their mother did not show any characteristic of a carrier despite the pluridimensional investigations including electron microscopy. The authors suggest in this situation a point mutation before the first cellular division at the origin of the gestation of the two dystrophic twins. However, there is also the possibility that the mother of the twins is a heterozygote in whom the carrier state could not be diagnosed by the available methods.

     

Polymères α,α'-diméthylxylyléniques, 3. Copolycondensation du bis(chloro-1 éthyl)-1,4 benzène avec des hydrocarbures aromatiques mononucléaires

Copolycondensation reactions of 1,4-bis(1-chloroethyl)benzene with benzene, toluene, m- and p-xylene, mesitylene, and 1,2,4,5-tetramethylbenzene were studied. These reactions afford products with tridimensional structures not melting and only partially soluble even in the case of 1,2,4,5-tetramethylbenzene where a linear product was to be expected.     

Stability Study of the Irradiated Poly(lactic acid)/Styrene Isoprene Styrene Reinforced with Silica Nanoparticles

In this paper, the stability improvement of poly(lactic acid) (PLA)/styrene-isoprene block copolymer (SIS) loaded with silica nanoparticles is characterized. The protection efficiency in the material of thermal stability is mainly studied by means of high accurate isothermal and nonisothermal chemiluminescence procedures. The oxidation induction times obtained in the isothermal CL determinations increase from 45 min to 312 min as the polymer is free of silica or the filler loading is about 10%, respectively. The nonisothermal measurements reveal the values of onset oxidation temperatures with about 15% when the concentration of SiO₂ particles is enhanced from none to 10%. The curing assay and Charlesby–Pinner representation as well as the modifications that occurred in the FTIR carbonyl band at 1745 cm⁻¹ are appropriate proofs for the delay of oxidation in hybrid samples. The improved efficiency of silica during the accelerated degradation of PLA/SIS 30/n-SiO₂ composites is demonstrated by means of the increased values of activation energy in correlation with the augmentation of silica loading. While the pristine material is modified by the addition of 10% silica nanoparticles, the activation energy grows from 55 kJ mol⁻¹ to 74 kJ mol⁻¹ for nonirradiated samples and from 47 kJ mol⁻¹ to 76 kJ mol⁻¹ for γ-processed material at 25 kGy. The stabilizer features are associated with silica nanoparticles due to the protection of fragments generated by the scission of hydrocarbon structure of SIS, the minor component, whose degradation fragments are early converted into hydroperoxides rather than influencing depolymerization in the PLA phase. The reduction of the transmission values concerning the growing reinforcement is evidence of the capacity of SiO₂ to minimize the changes in polymers subjected to high energy sterilization. The silica loading of 10 wt% may be considered a proper solution for attaining an extended lifespan under the accelerated degradation caused by the intense transfer of energy, such as radiation processing on the polymer hybrid.     

Medial epicondyle osteotomy: a method of choice in severe varus knee arthroplasty

The purpose of this study was to evaluate the results of total knee arthroplasty (TKA) after using medial epicondyle osteotomy (MEO) as a balancing method for severe varus deformity and also to compare these results with those of TKA after using additional resection of the tibial medial plateau to correct this deformity. A total of 60 knees with severe varus deformity underwent TKA between 2006 and 2010. In 30 cases, we used MEO as a balancing method, and in other 30, additional medial tibial plateau resection was performed. The clinical outcomes were measured with the Knee Society score (KSS), the range of the motion and frontal laxity of the knee. The radiological outcomes were measured by anteroposterior simple radiographs to assess: the union state of the osteotomy site, the amount of resected tibial medial plateau bone and the femorotibial angle. The findings of the study show that in the MEO group the KSS improved from 21.13?±?13.6 to 92.1?±?7.6 points (P?<?0.001). Moreover, the range of motion increased from 70.3°?±?25.3° to 109.3°?±?12.7° (P?<?0.001). The femorotibial angle was corrected from a 22.6°?±?5.71° varus to a 4.0°?±?1.38° valgus (P?<?0.001) and frontal laxity decreased from 10.83°?±?3.9° to 0.33°?±?1.2° (P?<?0.001). No statistically significant differences were found between groups regarding the postoperative outcomes of KSS, range of motion, femorotibial angle and frontal laxity. The amount of resected tibial medial plateau bone was statistically significantly smaller in the MEO group (1.63?±?0.96?mm in the MEO group and 4.73?±?2.7?mm in the other group; P?<?0.001). In the MEO group, the mean thickness of the polyethylene insert was 12.66?±?1.21?mm, while in the second group, it was 13.73?±?1.59?mm, with statistically significant P?=?0.005. Fibrous union occurred in all knees in the MEO group. Using medial epicondyle osteotomy for varus knee when performing total knee arthroplasty could be a useful ligament-balancing technique to achieve medial stability of the knee. In addition, it could have considerable advantages towards the additional resection of the tibial medial plateau.