Synthesis of Small‐Sized,Porous, and Low‐Toxic Magnetite Nanoparticles by Thin POSS Silica Coating

In this communication, we report the synthesis of small‐sized (<10 nm), water‐soluble, magnetic nanoparticles (MNPs) coated with polyhedral oligomeric silsesquioxanes (POSS), which contain either polyethylene glycol (PEG) or octa(tetramethylammonium) (OctaTMA) as functional groups. The POSS‐coated MNPs exhibit superparamagnetic behavior with saturation magnetic moments (51–53 emu g^?1) comparable to silica‐coated MNPs. They also provide good colloidal stability at different pH and salt concentrations, and low cytotoxicity to MCF‐7 human breast epithelial cells. The relaxivity data and magnetic resonance (MR) phantom images demonstrate the potential application of these MNPs in bioimaging.     

A solution of the DGLAP equation for gluon at low x

We obtain a solution of the DGLAP equation for the gluon at low x first by expanding the gluon in a Taylor series and then using the method of characteristics. We test its validity by comparing it with that of Glück, Reya and Vogt. The convergence criteria of the approximation used are also discussed. We also calculate εF ₂(x,Q)²/ε In Q ² using its approximate relations with the gluon distribution at low x. The predictions are then compared with the HERA data.     

Another independent self-dual basis for the trivial variety

We give a new independent self-dual 3-basis for the trivial variety with two binary operations. Received October 24, 2006; accepted in final form January 25, 2007.     

Uncertainty principle and the horizon size of our universe

Quantum uncertainties prevent simultaneous measurement of the expansion factor S(t) and its time derivative . Consequently the Hubble size has an inherent uncertainty in the quantum state that describes the semiclassical evolution of the universe. We show that the quantum uncertainty in the Hubble size of the universe is amplified to unacceptably large values in any inflationary process.This essay received an honorable mention from the Gravity Research Foundation, 1986-Ed.     

Aromatic-aromatic interactions in crystal structures of helical peptide scaffolds containing projecting phenylalanine residues

Aromatic-aromatic interactions between phenylalanine side chains in peptides have been probed by the structure determination in crystals of three peptides: Boc-Val-Ala-Phe-Aib-Val-Ala-Phe-Aib-OMe, I; Boc-Val-Ala-Phe-Aib-Val-Ala-Phe-Aib-Val-Ala-Phe-Aib-OMe, II; Boc-Aib-Ala-Phe-Aib-Phe-Ala-Val-Aib-OMe, III. X-ray diffraction studies reveal that all three peptides adopt helical conformations in the solid state with the Phe side chains projecting outward. Interhelix association in the crystals is promoted by Phe-Phe interactions. A total of 15 unique aromatic pairs have been characterized in the three independent crystal structures. In peptides I and II, the aromatic side chains lie on the same face of the helix at i/i + 4 positions resulting in both intrahelix and interhelix aromatic interactions. In peptide III, the Phe side chains are placed on the opposite faces of the helix, resulting in exclusive intermolecular aromatic interactions. The distances between the centroids of aromatic pair ranges from 5.11 to 6.86 A, while the distance of closest approach of ring carbon atoms ranges from 3.27 to 4.59 A. Examples of T-shaped and parallel-displaced arrangements of aromatic pairs are observed, in addition to several examples of inclined arrangements. The results support the view that the interaction potential for a pair of aromatic rings is relatively broad and rugged with several minima of similar energies, separated by small activation barriers.     

Regio- and stereoselective synthesis of E-1,3-enynes via coupling of nucleophiles with 1-[(alkynyl) dicobalt hexacarbonyl]allyl cations

Reactions of the title complexes with the nucleophiles anisole, allyl silanes, isopropenyl acetate, and ethanol have been examined. The carbon nucleophiles react regio- and stereoselectively to give $\text{E}$-1,3-enyne derivatives.     

Binding constant measurement by hyper-Rayleigh scattering: bilirubin-human serum albumin binding as a case study

In this paper, a new application of the hyper-Rayleigh scattering technique in determining multiple binding constants of a small molecule like bilirubin to a macromolecule like the protein human serum albumin has been demonstrated. Human serum albumin has two binding sites for bilirubin, and the binding constants have been measured by carrying out a second harmonic titration of the protein against bilirubin and vice versa. The measured binding constants K(1) = 1.5 +/- 0.43 x 10(7) M(-1) and K(2) = 1.01 +/- 0.16 x 10(6) M(-1) agree well with the reported values obtained by other methods.