This paper describes the application of recently developed nuclear magnetic resonance (NMR) pulse sequences to obtain information about the internal dynamics of isotopically enriched hydrophobic side chains in proteins. The two-dimensional spectra provided by the pulse sequences enable one to make accurate measurements of nuclear Overhauser effects (NOE) and longitudinal (T1) and transverse (T2) relaxation times of enriched methyl carbons in proteins. Herein, these techniques are used to investigate the internal dynamics of the 11 leucine side chains of staphylococcal nuclease (SNase), a small enzyme having Mr = 16.8K, in the absence and presence of ligands thymidine 3',5'-bisphosphate (pdTp) and Ca2+. We report the synthesis of [5,5'-13C2]leucine, the preparation of SNase containing the labeled leucine, the sequential assignment of the leucine methyl carbons and protons in the liganded and unliganded proteins, and the measurement of the 13C T1, T2, and NOE values for the SNase leucine methyl carbons. Analysis of the relaxation parameters using the formalism of Lipari and Szabo shows that the internal motions of the leucine methyl carbons are characterized by effective correlation times tau f (5-80 ps) and tau s (less than 2 ns). The fast motion is identified with the rapid rotation of the methyl group about the C gamma-C delta bond axis, while the slow motion is associated with reorientation of the C gamma-C delta bond axis itself. The mean squared order parameters associated with the latter motion, Ss2, lie in the range 0.34-0.92. The values of Ss2 correlate reasonably well with the temperature factors of the leucine methyl carbons obtained from the crystal structures, but some are smaller than anticipated on the basis of the fact that nearly all leucine methyl carbons are buried and have temperature factors no larger than that of the leucine backbone atoms. Five leucine residues in liganded SNase and eight in unliganded SNase have values of Ss2 less than 0.71. These order parameters correspond to large amplitude motions (angular excursions of 27-67 degrees) of the C gamma-C delta bond axis. These results indicate that, in solution, the internal motions of the leucine side chains of SNase are significantly larger than suggested by the X-ray structures or by qualitative analysis of NOESY spectra. Comparison of Ss2 values obtained from liganded and unliganded SNase reveals a strong correlation between delta Ss2 and distance between the leucine methyl carbon and the ligands.(ABSTRACT TRUNCATED AT 400 WORDS)

<p>Este texto se propone reseñar de manera crítica tres esfuerzos investigativos que proponen cartografías sonoras de espacios urbanos en Bogotá, Cali y Medellín. Estos trabajos manifiestan una evolución conceptual de las prácticas artísticas asociadas a la valoración del paisaje sonoro y discuten, desde el arte, la arquitectura y la cinematografía interactiva asuntos como la escucha, la identidad cultural y el patrimonio inmaterial. A lo largo del texto serán examinados algunos de los principales conceptos que rodean el paisaje sonoro identificando sus gestores y su adopción en las prácticas sonoras en Colombia. Además, serán discutidos aspectos subjetivos e individuales de la escucha y su relación con el paisaje sonoro, lo cual permitirá reconocer el alcance de los proyectos y sus conexiones con algunas contingencias de las ciudades contemporáneas. El criterio de utilización de los medios fonográficos es también tomado como un asunto de interés artístico que evidencia la diversidad de intenciones y procedimientos en las prácticas de mapeo sonoro en el país.</p><p class="normal"> </p>

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This paper addresses a high-level discussion about the links between Science and Music, focusing on my own sonification and auditory display practices around air quality. Grounded on recent insights on interdisciplina- rity and sonification practices, the first sections will point out some potential contributions from scientific research to music studies and vice versa. I will propose the concept of mutualism to depict the interdependent status of Mu- sic and Science. The final sections will discuss air contamination as a complex contemporary problem, and will re- port three practice-based-design projects, AirQ jacket, Esmog Data and Breathe!, which outline different directions in facing local environmental awareness. 

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