Site-specific conjugation of 8-ethynyl-BODIPY to a protein by [2+3] cycloaddition

We report a straightforward synthesis of 8-ethynyl-BODIPY derivatives and their potential as fluorescent labeling compounds using an alkyne-azide click chemistry approach. The ethynyl substituted BODIPY dyes at the meso-position were reacted under Cu+ catalysis and mild physiological conditions in organic and biological model systems using benzyl azide and a Barstar protein which was selectively modified by a single amino acid substituted methionine at the N-terminus (Met1). azidohomoalanine (Aha). Conjugation with the protein and the model azide was indicated by a significant blue shift upon formation of the triazole moiety system, which allowed easy distinction between free and coupled dyes. This blue shift was rationalized by the perpendicular orientation of the triazole relative to the chromophore using time dependent density functional theory (TDDFT) calculations. A full spectroscopic and thermodynamic characterization of the protein revealed that a fluorophore was incorporated without the cross influence of protein stability and functional integrity. Furthermore, model reactions of 8-ethynyl-BODIPY derivatives with benzyl azide under copper-free conditions indicate second order kinetics with high rate constants comparable with those found for the strain-promoted azide-alkyne cycloaddition (SPAAC). In this way, we establish a unique and highly efficient method to introduce alkyne-BODIPY into a protein scaffold potentially useful for diverse applications in areas ranging from fundamental protein dynamics studies to biotechnology or cell biology

Electronic Shell Structure and Relative Abundances of Cesium-Coated C60

URL:http://link.aps.org/doi/10.1103/PhysRevLett.77.1127 DOI:10.1103/PhysRevLett.77.1127The relative abundances of C60Cs(N), N≤500, determined from mass spectra measurements, are presented and explained in terms of the successive filling of the electronic shells by the cesium valence electrons. The motion of the Cs valence electrons, confined to a metal layer surrounding the C60 molecule, is described within the jellium model, with Cs spread into a uniform positive background. The electronic shell structure is calculated with the local approximation to density-functional theory and is shown to correspond to measured abundances. Strong Friedel oscillations in the electronic density are found and closed forms for them are given for jellium spheres both with and without the void.M. S. and S. S. would like to thank the Research Board of the University of Missouri for partial financial assistance

Using the local density approximation and the LYP, BLYP, and B3LYP functionals within Reference--State One--Particle Density--Matrix Theory

For closed-shell systems, the local density approximation (LDA) and the LYP, BLYP, and B3LYP functionals are shown to be compatible with reference-state one-particle density-matrix theory, where this recently introduced formalism is based on Brueckner-orbital theory and an energy functional that includes exact exchange and a non-universal correlation-energy functional. The method is demonstrated to reduce to a density functional theory when the exchange-correlation energy-functional has a simplified form, i.e., its integrand contains only the coordinates of two electron, say r1 and r2, and it has a Dirac delta function -- delta(r1 - r2) -- as a factor. Since Brueckner and Hartree--Fock orbitals are often very similar, any local exchange functional that works well with Hartree--Fock theory is a reasonable approximation with reference-state one-particle density-matrix theory. The LDA approximation is also a reasonable approximation. However, the Colle--Salvetti correlation-energy functional, and the LYP variant, are not ideal for the method, since these are universal functionals. Nevertheless, they appear to provide reasonable approximations. The B3LYP functional is derived using a linear combination of two functionals: One is the BLYP functional; the other uses exact exchange and a correlation-energy functional from the LDA.Comment: 26 Pages, 0 figures, RevTeX 4, Submitted to Mol. Phy

Hydrogen atom in phase space. The Kirkwood-Rihaczek representation

We present a phase-space representation of the hydrogen atom using the Kirkwood-Rikaczek distribution function. This distribution allows us to obtain analytical results, which is quite unique because an exact analytical form of the Wigner functions corresponding to the atom states is not known. We show how the Kirkwood-Rihaczek distribution reflects properties of the hydrogen atom wave functions in position and momentum representations.Comment: 5 pages (and 5 figures

Ab initio many-body calculations on infinite carbon and boron-nitrogen chains

In this paper we report first-principles calculations on the ground-state electronic structure of two infinite one-dimensional systems: (a) a chain of carbon atoms and (b) a chain of alternating boron and nitrogen atoms. Meanfield results were obtained using the restricted Hartree-Fock approach, while the many-body effects were taken into account by second-order M{\o}ller-Plesset perturbation theory and the coupled-cluster approach. The calculations were performed using 6-31$G^{**}$ basis sets, including the d-type polarization functions. Both at the Hartree-Fock (HF) and the correlated levels we find that the infinite carbon chain exhibits bond alternation with alternating single and triple bonds, while the boron-nitrogen chain exhibits equidistant bonds. In addition, we also performed density-functional-theory-based local density approximation (LDA) calculations on the infinite carbon chain using the same basis set. Our LDA results, in contradiction to our HF and correlated results, predict a very small bond alternation. Based upon our LDA results for the carbon chain, which are in agreement with an earlier LDA calculation calculation [ E.J. Bylaska, J.H. Weare, and R. Kawai, Phys. Rev. B 58, R7488 (1998).], we conclude that the LDA significantly underestimates Peierls distortion. This emphasizes that the inclusion of many-particle effects is very important for the correct description of Peierls distortion in one-dimensional systems.Comment: 3 figures (included). To appear in Phys. Rev.

Linear-response theory and lattice dynamics: a muffin-tin orbital approach

A detailed description of a method for calculating static linear-response functions in the problem of lattice dynamics is presented. The method is based on density functional theory and it uses linear muffin-tin orbitals as a basis for representing first-order corrections to the one-electron wave functions. As an application we calculate phonon dispersions in Si and NbC and find good agreement with experiments.Comment: 18 pages, Revtex, 2 ps figures, uuencoded, gzip'ed, tar'ed fil

Nucleation of a sodium droplet on C60

We investigate theoretically the progressive coating of C60 by several sodium atoms. Density functional calculations using a nonlocal functional are performed for NaC60 and Na2C60 in various configurations. These data are used to construct an empirical atomistic model in order to treat larger sizes in a statistical and dynamical context. Fluctuating charges are incorporated to account for charge transfer between sodium and carbon atoms. By performing systematic global optimization in the size range 1<=n<=30, we find that Na_nC60 is homogeneously coated at small sizes, and that a growing droplet is formed above n=>8. The separate effects of single ionization and thermalization are also considered, as well as the changes due to a strong external electric field. The present results are discussed in the light of various experimental data.Comment: 17 pages, 10 figure

Using choir conducting to improve leadership practice

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Low-energy electronic states of carbon nanocones in an electric field

«Non v’è salvezza al di fuori del mostruoso»; «la diserzione, intrinseca alla letteratura, diventa nel fantastico sfida blasfema, obiezione, tradimento»: in questi passi, lo scrittore italiano Giorgio Manganelli (1922-1990) riafferma la portata trasgressiva della sua opera, indicando nel superamento dei limiti razionali, del verosimile, dell’accettabile o, in altre parole, del narrabile la via per sottrarre la letteratura ad una funzione strumentale. Così, nel privilegiarla come atto di linguaggio e nel disimpegnarla da mansioni mimetico-realistiche, Manganelli la popola di esseri informi e metamorfici. Ad esempio, in opere quali Hilarotragoedia (1964) e Dall’inferno (1985) il mostruoso non si presenta come qualcosa di aberrante, ma piuttosto come il risultato di una sorta di teologia paradossale, in grado di sovvertire o burlare le grandi convenzioni umane. Partendo da tali questioni, l’articolo affronterà il tema del mostro quale infrazione e sovversione essenziali allo scardinamento di un orizzonte ermeneutico antropocentrico, come voleva, tra gli altri, Foucault. «There is no salvation beyond the monstrous»; «desertion, intrinsic to literature, becomes in the Fantastic a blasphemous challenge, objection and betrayal»: with these words, the Italian writer Giorgio Manganelli (1922-1990) reaffirms the transgression of his work. With the overcoming of rational limits, of the plausible, of the acceptable or, in other words, of the tellable, the writer illustrates the way to prevent the use of literature as an instrumental function. Therefore, by using literature as an act of speech and by disengaging it from its mimetic-realistic responsibilities, Manganelli populates it with shapeless and metamorphic beings. In works such as Hilarotragoedia (1964) and From Hell (1985), for example, the monstrous does not resemble something aberrant, but rather it represents a kind of paradoxical theology, capable of subverting or mocking the great human convictions. Starting from these questions, this paper will approach the subject of the monster as infringement and subversion essential for the disruption of a hermeneutic and anthropocentric horizon, as Foucault, among others, wished