The looping probability of random heteropolymers helps to understand the scaling properties of biopolymers

Random heteropolymers are a minimal description of biopolymers and can provide a theoretical framework to the investigate the formation of loops in biophysical experiments. A two--state model provides a consistent and robust way to study the scaling properties of loop formation in polymers of the size of typical biological systems. Combining it with self--adjusting simulated--tempering simulations, we can calculate numerically the looping properties of several realizations of the random interactions within the chain. Differently from homopolymers, random heteropolymers display at different temperatures a continuous set of scaling exponents. The necessity of using self--averaging quantities makes finite--size effects dominant at low temperatures even for long polymers, shadowing the length--independent character of looping probability expected in analogy with homopolymeric globules. This could provide a simple explanation for the small scaling exponents found in experiments, for example in chromosome folding

Influence of Anti-CD44 on Murine B Cell Activation

Lymphocyte activation and trafficking are indispensable to the immune system. CD44, an adhesion molecule, plays important roles in T cell activation, lymphocyte homing/trafficking, and tumor metastasis. Although the functions of CD44 have been shown in T cells and other leukocytes, little is known about its role in B cells. The effects of CD44 cross-linking on murine B cell activation via CD40L/IL-4 was explored using the anti-CD44 mAbs RK3G9 and IM7. Immobilized RK3G9 and IM7 could strongly inhibit B cell proliferation and Ig production, with IgE inhibition being prominent. Soluble anti-CD44 had no effect. The inhibitory effect of RK3G9 was not influenced by addition of anti-FCγRII, indicating no role for the inhibitory receptor. The effects of delayed addition of immobilized anti-CD44 mAbs were studied, and the results indicated no inhibition after 96 hrs of culture. B cells were also activated by either LPS or anti-IgM F(ab\u27)2. While LPS-induced B cell activation was inhibited by immobilized anti-CD44 mAbs, anti-IgM activation was refractory. Interestingly, addition of both anti-IgM and CD40L or LPS resulted in some modulation of the inhibitory activity. Additionally, FACS and Elispot revealed that RK3G9-treated cells had reduced numbers of plasma cells. Taken together, these results suggest that CD44 cross-linking could control polyclonal B cell activation by CD40L, but allow sIgM/CD40L activation to continue

Drawing Doctors vs. Nurses: Gendered Perceptions of Health Professionals

Although women and men are employed at similar rates, there remains a high level of occupational sex segregation. Existing gender stereotypes influence occupational choice because of gendered perceptions of occupations. In this study, college students (n = 48) were asked to draw a picture of an individual in a gender-typed health profession—either a doctor or a nurse—using a variation of the Draw-a- Scientist paradigm. Using quantitative and qualitative techniques, we find that doctors are drawn as women nearly as often as men, while nurses are drawn as women far more frequently than they are as men. Doctors are far more likely to be illustrated wearing white coats and stethoscopes, while nurses are shown wearing scrubs and using other medical paraphernalia in addition to stethoscopes. Finally, nurses are far more likely to be shown with their patients and to be described as helping others. Our findings provide key details related to presentational expectations for doctors and nurses, which in turn have important implications for occupational sex segregation. In other words, our data demonstrate which types of impression management (particularly attire, objects, and setting) individuals consider to be crucial signifiers for nurses and doctors, which may also influence their occupational choices

PENGARUH STRATEGI GUIDED DISCOVERY LEARNING TERHADAP KEMAMPUAN BERPIKIR KRITIS PADA PEMBELAJARAN IPA SISWA KELAS V SEKOLAH DASAR

: Research experiment this intent to know influence strategy guided discoverylearning to Ability think critical on learning Natural sciences student class V Elementary School. Sample in research this are student class V Elementary school Jakarta East as much 80 student. Take sample utilize tech cluster randomsampling.Method one that utilized are methodic experiment, with design research pretest post test control group design. Data collecting done with Utilize essay form breakdown of,.Base resultcountquiz t, gotten thitung's price > t tabel which is 5,95> 1,67, therefore H0 refused and H1 accepted. Result research points out that strategy guided discovery learning having for signifikan to Ability think critical on student Natural Sciences learning brazes v Elementary School. This result points out that strategy guided discovery learning can made as incorrectly one alternative in develop ability think critical student brazes v Elementary School

What thermodynamic features characterize good and bad folders? Results from a simplified off-lattice protein model

The thermodynamics of the small SH3 protein domain is studied by means of a simplified model where each bead-like amino acid interacts with the others through a contact potential controlled by a 20x20 random matrix. Good folding sequences, characterized by a low native energy, display three main thermodynamical phases, namely a coil-like phase, an unfolded globule and a folded phase (plus other two phases, namely frozen and random coil, populated only at extremes temperatures). Interestingly, the unfolded globule has some regions already structured. Poorly designed sequences, on the other hand, display a wide transition from the random coil to a frozen state. The comparison with the analytic theory of heteropolymers is discussed

Equilibrium properties of realistic random heteropolymers and their relevance for globular and naturally unfolded proteins

Random heteropolymers do not display the typical equilibrium properties of globular proteins, but are the starting point to understand the physics of proteins and, in particular, to describe their non-native states. So far, they have been studied only with mean-field models in the thermodynamic limit, or with computer simulations of very small chains on lattice. After describing a self-adjusting parallel-tempering technique to sample efficiently the low-energy states of frustrated systems without the need of tuning the system-dependent parameters of the algorithm, we apply it to random heteropolymers moving in continuous space. We show that if the mean interaction between monomers is negative, the usual description through the random energy model is nearly correct, provided that it is extended to account for non-compact conformations. If the mean interaction is positive, such a simple description breaks out and the system behaves in a way more similar to Ising spin glasses. The former case is a model for the denatured state of glob- ular proteins, the latter of naturally-unfolded proteins, whose equilibrium properties thus result qualitatively different

Use of the Metropolis algorithm to simulate the dynamics of protein chains

The Metropolis implementation of the Monte Carlo algorithm has been developed to study the equilibrium thermodynamics of many-body systems. Choosing small trial moves, the trajectories obtained applying this algorithm agree with those obtained by Langevin's dynamics. Applying this procedure to a simplified protein model, it is possible to show that setting a threshold of 1 degree on the movement of the dihedrals of the protein backbone in a single Monte Carlo step, the mean quantities associated with the off-equilibrium dynamics (e.g., energy, RMSD, etc.) are well reproduced, while the good description of higher moments requires smaller moves. An important result is that the time duration of a Monte Carlo step depends linearly on the temperature, something which should be accounted for when doing simulations at different temperatures.Comment: corrections to the text and to the figure