Phase Diagram of alpha-Helical and beta-Sheet Forming Peptides

The intrinsic property of proteins to form structural motifs such as alpha-helices and beta-sheets leads to a complex phase behavior in which proteins can assemble into various types of aggregates including crystals, liquidlike phases of unfolded or natively folded proteins, and amyloid fibrils. Here we use a coarse-grained protein model that enables us to perform Monte Carlo simulations for determining the phase diagram of natively folded alpha-helical and unfolded beta-sheet forming peptides. The simulations reveal the existence of various metastable peptide phases. The liquidlike phases are metastable with respect to the fibrillar phases, and there is a hierarchy of metastability

Nucleation of amyloid fibrils

We consider nucleation of amyloid fibrils in the case when the process occurs by the mechanism of direct polymerization of practically fully extended protein segments, i.e. beta-strands, into beta-sheets. Applying the classical nucleation theory, we derive a general expression for the work to form a nanosized amyloid fibril (protofilament) constituted of successively layered beta-sheets. Analysis of this expression reveals that with increasing its size, the fibril transforms from one-dimensional into two-dimensional aggregate in order to preserve the equilibrium shape corresponding to minimal formation work. We determine the size of the fibril nucleus, the fibril nucleation work and the fibril nucleation rate as explicit functions of the concentration and temperature of the protein solution. The results obtained are applicable to homogeneous nucleation which occurs when the solution is sufficiently pure and/or strongly supersaturated

Poisoning from stings by marine animals in the Black Sea

The sea represents one separate world, individual ecosystem, a habitat of a great variety of organisms. It brings health and satisfaction. Everyone who takes advantage of the natural wealth must also be aware of its risks and dangers. Part of them are related to the incidents by marine animals. The poisonous marine creatures are a huge diversity. They cause injuries mostly in the warm seas.The fauna of the Black Sea consists of 1966 species. Among them there are some who are claimed to be dangerous for the people because of the toxic substances they excrete while stinging.The aim of the present work is to analyse the risks of stinging by marine organisms in the Black Sea.Results: The most striking examples, representative of the hazardous species in the Black Sea are the following: The greater weever (Trachinus draco), The black scorpionfish, Scorpaenidae (Scorpaena porcus), The common stingray (Dasyatis pastinaca), Atlantic stargazer (Uranoscopus scaber), The Eurasian ruffe, ruffe, pope (Gymnocephalus cernuus), Jellyfish (Aurelia aurita, Rizozoma pulmo и Мnemiopsis leydi), The Hydrophiinae - also known as coral reef snakes or sea snakes, are one of the most toxic, but in our sea are absolutely harmless. Their toxic effects can be local - severe pain, local erythema and oedema; general - weakness, headache, malaise and neurological symptoms. Different allergic reactions, from urticaria and angioedema to anaphylactic shock (rarely), are possible.Conclusion: The Black Sea is one of the most friendly and safest seas. However, in order to stay healthy and secure people should be well aware of its great powers, possibilities and dangers together with its priceless benefits. In this way they would be able to make the most of it and enjoy it

New critical behavior in unconventional ferromagnetic superconductors

New critical behavior in unconventional superconductors and superfluids is established and described by the Wilson-Fisher renormalization-group method. For certain ordering symmetries a new type of fluctuation-driven first order phase transitions at finite and zero temperature are predicted. The results can be applied to a wide class of ferromagnetic superconducting and superfluid systems, in particular, to itinerant ferromagnets as UGe2 and URhGe.Comment: 12 pages, 6 fig

Approaching equilibrium and the distribution of clusters

We investigate the approach to stable and metastable equilibrium in Ising models using a cluster representation. The distribution of nucleation times is determined using the Metropolis algorithm and the corresponding $\phi^{4}$ model using Langevin dynamics. We find that the nucleation rate is suppressed at early times even after global variables such as the magnetization and energy have apparently reached their time independent values. The mean number of clusters whose size is comparable to the size of the nucleating droplet becomes time independent at about the same time that the nucleation rate reaches its constant value. We also find subtle structural differences between the nucleating droplets formed before and after apparent metastable equilibrium has been established.Comment: 22 pages, 16 figure

Chemical Composition and Energy Nutritional Value of the Meat of Guinea Fowls (Numidameleagris), Fattened to different Ages

The aim of the study was to investigate the chemical composition and energy content of the meat of young Guinea-fowls, with different duration of the fattening period, raised in a free-range, semi-intensive production system. The authors establish the following data: dry matter content- from 27.08 to 28.82% in breast muscle and from 23.83 to 26.56% in thigh muscle; crude protein in dry matter –from 86.19to 93.54% in breastand from 82.02 to 87.84% in thigh muscle; crude fat in dry matter - from 5.64 to 7.58% in breast and from 9.02 to 11.05% in thigh muscles. The average energy content in 100 g dry matter varies from 23.7 (breast muscle, 16 weeks of age) to 25.07 kJ (thigh muscle, 24 weeks of age)

Diamagnetic susceptibility of spin-triplet ferromagnetic superconductors

We calculate the diamagnetic susceptibility in zero external magnetic field above the phase transition from ferromagnetic phase to phase of coexistence of ferromagnetic order and unconventional superconductivity. For this aim we use generalized Ginzburg-Landau free energy of unconventional ferromagnetic superconductor with spin-triplet electron pairing. A possible application of the result to some intermetallic compounds is briefly discussed.Comment: 7 pages, 1 figur

In vitro evaluation of the antimicrobial properties of Mallotus oppositifolium decoction leaf extracts and fractions

In order to verify the in vitro antimicrobial properties of Mallotus oppositifolium (Euphorbiaceae), the qualitative phytochemical screening and the antimicrobial activities on Shigella dysenteriae A2, Salmonella typhi, Escherichia coli, Enterococcus faecalis, Staphyllococcus aureus and Candida albicans strains of the aqueous decoction (DEMO) hexane (HEMO) and methanol (MEMO) fractions of leaves were assessed. The screening was performed using colorimetric methods. The antimicrobial activity was carried out using disc diffusion assays. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were determined by the dilution methods. The screening revealed the presence of metabolites such as alkaloids, flavonoids, phenolic compounds, tannins, saponins, lipids, carbohydrates, mucilages, proteins, triterpens and steroids. DEMO, HEMO, MEMO showed a concentration-dependent activity against Shigella dysenteriae A2 and Salmonella typhi, with inhibition zone ranging from 9.44±0.44 to 19.00±0.24 mm, 8.94±0.05 to 20.03±0.17 mm and 8.13±0.17 to 16.76±0.11 mm respectively. The MIC showed ranges from 0.25 to 1.00 mg.mL-1, 0.20 to 0.50 mg.mL-1 and 1.00 to 3.00 mg.mL-1, while the MBC ranged from 1.00 to 5.00 mg.mL-1, 0.50 to 1.00 and 3.00 to 10.00 mg.mL-1 respectively. The leaves decoction and fractions activity on the two strains showed promising activities to justify the use of the plant against diarrhoea in folk medicine.Keywords: Folk medicine, phytochemical analysis, Mallotus oppositifolium diarrhea, antimicrobial

Meissner phases in spin-triplet ferromagnetic superconductors

We present new results for the properties of phases and phase transitions in spin-triplet ferromagnetic superconductors. The superconductivity of the mixed phase of coexistence of ferromagnetism and unconventional superconductivity is triggered by the presence of spontaneous magnetization. The mixed phase is stable but the other superconducting phases that usually exist in unconventional superconductors are either unstable or for particular values of the parameters of the theory some of them are metastable at relatively low temperatures in a quite narrow domain of the phase diagram. Phase transitions from the normal phase to the phase of coexistence is of first order while the phase transition from the ferromagnetic phase to the coexistence phase can be either of first or second order depending on the concrete substance. Cooper pair and crystal anisotropies determine a more precise outline of the phase diagram shape and reduce the degeneration of ground states of the system but they do not change drastically phase stability domains and thermodynamic properties of the respective phases. The results are discussed in view of application to metallic ferromagnets as UGe2, ZrZn2, URhGe.Comment: 21 pages, 7 figures; Phys. Rev. B (2005) in pres