Functionalization of thioctic acid-capped gold nanoparticles for specific immobilization of histidine-tagged proteins

This paper presents an efficient strategy for the specific immobilization of fully functional proteins onto the surface of nanoparticles. Thioctic acid-derivatized gold clusters are used as a scaffold for further stepwise modification, leading to a cobalt(II)-terminated ligand shell. A histidine tag introduced by genetic engineering into a protein is coordinated to this transition metal ion. The specific immobilization has been demonstrated for the cases of a genetically engineered horseradish peroxidase and ferredoxin-NADP(+) reductase, confirming the attachment of the fully functional proteins to the Co(II)-terminated nanointerface. The absence of nonspecific protein adsorption and the specificity of the binding site have been verified using several analogues of the enzymes without the histidine tag.     

Correlation of delocalization indices and current-density maps in polycyclic aromatic hydrocarbons

Using multicentre delocalization indices, the ring current maps of a large set of polycyclic aromatic hydrocarbons (PAH) are reconstructed and compared with ab initio computations of the same maps in the pseudo-pi version of the ipsocentric approach to magnetic response. The quality of the comparison indicates that both delocalization and ring current approaches capture the same information about the aromatic nature of the PAH. Aromaticity as a global property, requires knowledge of more than single circuits, but the present results suggest no need to introduce a "multidimensional character" for aromaticity.     

Radical CH Alkylation of BODIPY Dyes Using Potassium Trifluoroborates or Boronic Acids

A one‐step synthetic procedure for the radical C?H alkylation of BODIPY dyes has been developed. This new reaction generates alkyl radicals through the oxidation of boronic acids or potassium trifluoroborates and allows the synthesis of mono‐, di‐, tri‐, and tetraalkylated fluorophores in a good to excellent yield for a broad range of organoboron compounds. Using this protocol, multiple bulky alkyl groups can be introduced onto the BODIPY core thus creating solid‐state emissive BODIPY dyes.     

Radical CH Arylation of the BODIPY Core with Aryldiazonium Salts: Synthesis of Highly Fluorescent Red‐Shifted Dyes

We describe herein the first radical C? H arylation of BODIPY dyes. This novel, general, one‐step synthetic procedure uses ferrocene to generate aryl radical species from aryldiazonium salts and allows the straightforward synthesis of brightly fluorescent (Φ>0.85) 3,5‐diarylated and 3‐monoarylated boron dipyrrins in up to 86 % yield for a broad range of aryl substituents. In this way, new and complex dyes with red‐shifted spectra can be easily prepared.     

Metalloenzyme‐Like Zeolites as Lewis Acid Catalysts for CC Bond Formation

The use of metalloenzyme‐like zeolites as Lewis acid catalysts for C? C bond formation reactions has received increasing attention over the past few years. In particular, the observation of direct aldol condensation reactions enabled by hydrophobic zeolites with isolated framework metal sites has encouraged the development of catalytic approaches for producing chemicals from biomass‐derived compounds. The discovery of new Diels–Alder cycloaddition/dehydration routes and experimental and computational studies of Lewis acid catalyzed carbonyl–ene reactions have given a further boost to this rapidly evolving field.     

Packing list-colorings

List coloring is an influential and classic topic in graph theory. We initiate the study of a natural strengthening of this problem, where instead of one list-coloring, we seek many in parallel. Our explorations have uncovered a potentially rich seam of interesting problems spanning chromatic graph theory. Given a $k$-list-assignment $L$ of a graph $G$, which is the assignment of a list $L(v)$ of $k$ colors to each vertex $v\in V(G)$, we study the existence of $k$ pairwise-disjoint proper colorings of $G$ using colors from these lists. We may refer to this as a list-packing. Using a mix of combinatorial and probabilistic methods, we set out some basic upper bounds on the smallest $k$ for which such a list-packing is always guaranteed, in terms of the number of vertices, the degeneracy, the maximum degree, or the (list) chromatic number of $G$. (The reader might already find it interesting that such a minimal $k$ is well defined.) We also pursue a more focused study of the case when $G$ is a bipartite graph. Our results do not yet rule out the tantalising prospect that the minimal $k$ above is not too much larger than the list chromatic number. Our study has taken inspiration from study of the strong chromatic number, and we also explore generalizations of the problem above in the same spirit.     

Asymptotics of waiting time distributions in the accumulating priority queue

Queueing Systems - We analyze the asymptotics of waiting time distributions in the two-class accumulating priority queue with general service times. The accumulating priority queue was suggested by...     

Ambient Bistable Single Dipole Switching in a Molecular Monolayer

Reported here is a molecular dipole that self‐assembles into highly ordered patterns at the liquid‐solid interface, and it can be switched at room temperature between a bright and a dark state at the single‐molecule level. Using a scanning tunneling microscope (STM) under suitable bias conditions, binary information can be written at a density of up to 41 Tb cm^?2 (256 Tb/in²). The written information is stable during reading at room temperature, but it can also be erased at will, instantly, by proper choice of tunneling conditions. DFT calculations indicate that the contrast and switching mechanism originate from the stacking sequence of the molecular dipole, which is reoriented by the electric field between the tip and substrate.