Backbone dynamics of the cytotoxic Ribonuclease α-sarcin by 15N NMR

The cytotoxic ribonuclease α-sarcin is a 150-residue protein that inactivates ribosomes by selectively cleaving a single phosphodiester bond in a strictly conserved rRNA loop. In order to gain insights on the molecular basis of its highly specific activity, we have previously determined its solution structure and studied its electrostatics properties. Here, we complement those studies by analysing the backbone dynamics of α-sarcin through measurement of longitudinal relaxation rates R1, off resonance rotating frame relaxation rates R1ρ, and the 15N{1H} NOE of the backbone amide 15N nuclei at two different magnetic field strengths (11.7 and 17.6 T). The two sets of relaxation parameters have been analysed in terms of the reduced spectral density mapping formalism, as well as by the model-free approach. α-Sarcin behaves as an axial symmetric rotor of the prolate type (D /D⊥ = 1.16 ± 0.02) which tumbles with a correlation time τm of 7.54 ± 0.02 ns. The rotational diffusion properties have been also independently evaluated by hydrodynamic calculations and are in good agreement with the experimental results. The analysis of the internal dynamics reveals that α-sarcin is composed of a rigid hydrophobic core and some exposed segments which undergo fast (ps to ns) internal motions. Slower motions in the μs to ms time scale are less abundant and in some cases can be assigned to specific motional processes. All dynamic data are discussed in relation to the role of some particular residues of α-sarcin in the process of recognition of its ribosomal target

Flórula ruderal da cidade de Lavras, MG Ruderal plants from Lavras, MG

Efetuou-se o levantamento e a identificação das plantas ruderais ocorrentes na cidade de Lavras, MG. Foram identificadas 175 espécies, representando 122 gêneros, pertencentes a 41 famílias. As famílias. Compositae, Leguminosae, Graminese, Malvaceae, Convolvulaceae, Cyperaceae, Euphorbiaceae e Amaranthaceae, são as que apresentaram o maior número de espécies. O material foi coletado em áreas ajardinadas, beiras de caminhos, calçadas, muros e cercas, e em terrenos baldios.<br>A survey and identification of ruderal plants occuring in Lavras City, state of Minas Gerais, Brazil, was carried out. One hundred and seventy five species, representing 122 genera belonging to 41 families were indentified. Families Compositae, Leguminosae, Gramineae, Malvaceae, Convolvulaceae, Cyperaceae, Euphorbiaceae, and Amaranthaceae presented the greatest numbers of species among all families. All plant materials were collected in garden areas, along roadsides and streets, walls and fences, and wastelands