Simultaneous Identification of Spectral Properties and Sizes of Multiple Particles in Solution with Subnanometer Resolution

We report an unsurpassed solution characterization technique based on analytical ultracentrifugation, which demonstrates exceptional potential for resolving particle sizes in solution with sub-nm resolution. We achieve this improvement in resolution by simultaneously measuring UV/Vis spectra while hydrodynamically separating individual components in the mixture. By equipping an analytical ultracentrifuge with a novel multi-wavelength detector, we are adding a new spectral discovery dimension to traditional hydrodynamic characterization, and amplify the information obtained by orders of magnitude. We demonstrate the power of this technique by characterizing unpurified CdTe nanoparticle samples, avoiding tedious and often impossible purification and fractionation of nanoparticles into apparently monodisperse fractions. With this approach, we have for the first time identified the pure spectral properties and band-gap positions of discrete species present in the CdTe mixture.

Multidimensional analysis of nanoparticles with highly disperse properties using multiwavelength analytical ultracentrifugation

The worldwide trend in nanoparticle technology toward increasing complexity must be directly linked to more advanced characterization methods of size, shape and related properties, applicable to many different particle systems in science and technology. Available techniques for nanoparticle characterization are predominantly focused on size characterization. However, simultaneous size and shape characterization is still an unresolved major challenge. We demonstrate that analytical ultracentrifugation with a multiwavelength detector is a powerful technique to address multidimensional nanoparticle analysis. Using a high performance optical setup and data acquisition software, information on size, shape anisotropy and optical properties were accessible in one single experiment with unmatched accuracy and resolution. A dynamic rotor speed gradient allowed us to investigate broad distributions on a short time scale and differentiate between gold nanorod species including the precise evaluation of aggregate formation. We report how to distinguish between different species of single-wall carbon nanotubes in just one experiment using the wavelength-dependent sedimentation coefficient distribution without the necessity of time-consuming purification methods. Furthermore, CdTe nanoparticles of different size and optical properties were investigated in a single experiment providing important information on structure-property relations. Thus, multidimensional information on size, density, shape and optical properties of nanoparticulate systems becomes accessible by means of analytical ultracentrifugation equipped with multiwavelength detection.

The Open AUC Project

Progress in analytical ultracentrifugation (AUC) has been hindered by obstructions to hardware innovation and by software incompatibility. In this paper, we announce and outline the Open AUC Project. The goals of the Open AUC Project are to stimulate AUC innovation by improving instrumentation, detectors, acquisition and analysis software, and collaborative tools. These improvements are needed for the next generation of AUC-based research. The Open AUC Project combines on-going work from several different groups. A new base instrument is described, one that is designed from the ground up to be an analytical ultracentrifuge. This machine offers an open architecture, hardware standards, and application programming interfaces for detector developers. All software will use the GNU Public License to assure that intellectual property is available in open source format. The Open AUC strategy facilitates collaborations, encourages sharing, and eliminates the chronic impediments that have plagued AUC innovation for the last 20 years. This ultracentrifuge will be equipped with multiple and interchangeable optical tracks so that state-of-the-art electronics and improved detectors will be available for a variety of optical systems. The instrument will be complemented by a new rotor, enhanced data acquisition and analysis software, as well as collaboration software. Described here are the instrument, the modular software components, and a standardized database that will encourage and ease integration of data analysis and interpretation software.

A comparison of some of the cardiovascular risk factors in vegetarian and omnivorous Turkish females

BACKGROUND

Elevated serum total homocysteine (tHcy) is associated with an increased risk of cardiovascular disease. Homocysteine levels may be influenced by dietary habits. The aim of the present study was to determine the effects of a vegetarian diet on some of the cardiovascular risk factors in Turkish females.

METHOD

The study was conducted on 26 vegetarian and 26 omnivore females. Serum tHcy, folate, vitamin B(12) and lipids were determined and dietary data were assessed using a 4-day food intake record at two time points.

RESULTS

Compared with omnivores, vegetarians had higher plasma tHcy, 10.8 +/- 3.72 versus 12.6 +/- 5.97, (P < 0.05) and folate (P < 0.05) levels. The prevalence of hyperhomocysteinaemia was higher in vegetarians than in omnivores (34.6% versus 12.0%). In addition, serum vitamin B(12) levels were lower in vegetarians than in omnivores (P < 0.05). In vegetarians, significant inverse correlation was found between tHcy and serum vitamin B(12) levels (r = -0.969, P = 0.001).

CONCLUSION

The higher prevalence of mild hyperhomocysteinaemia in vegetarians indicated a diminished protective effect of vegetarian nutrition in cardiovascular disease prevention.