A linear-algebra problem from algebraic coding theory

Given an m×n matrix M over E=GF(q^t) and an ordered basis A={z₁,…,z_t} for field E over K=GF(q), expand each entry of M into a t×1 vector of coordinates of this entry relative to A to obtain an mt×n matrix M¹ with entries from the field K. Let r=rank(M) and r¹=rank(M¹). We show that r?r¹?min{rt,n}, and we determine the number b(m,n,r,r¹,q,t) of m×n matrices M of rank r over GF(q^t) with associated mt×n matrix M¹ of rank r¹ over GF (q).     

Utility of lab-on-a-chip technology for high-throughput nucleic acid and protein analysis

On-chip electrophoresis can provide size separations of nucleic acids and proteins similar to more traditional slab gel electrophoresis. Lab-on-a-chip (LoaC) systems utilize on-chip electrophoresis in conjunction with sizing calibration, sensitive detection schemes, and sophisticated data analysis to achieve rapid analysis times (<120 s). This work describes the utility of LoaC systems to enable and augment systems biology investigations. RNA quality, as assessed by an RNA integrity number score, is compared to existing quality control (QC) measurements. High-throughput DNA analysis of multiplex PCR samples is used to stratify gene sets for disease discovery. Finally, the applicability of a high-throughput LoaC system for assessing protein purification is demonstrated. The improvements in workflow processes, speed of analysis, data accuracy and reproducibility, and automated data analysis are illustrated.     

Mössbauer studies of the iron-sulfur cluster-free hydrogenase: the electronic state of the mononuclear Fe active site

The iron-sulfur cluster-free hydrogenase (Hmd) from methanogenic archaea harbors an iron-containing, light-sensitive cofactor of still unknown structure as prosthetic group. The enzyme is reversibly inhibited by CO and cyanide and is EPR silent. We report here on M?ssbauer spectra of the (57)Fe-labeled enzyme and of the isolated cofactor. The spectrum of the holoenzyme measured at 80 K revealed a doublet peak with an isomer shift delta = 0.06 mm.s(-)(1) and a quadrupole splitting of DeltaE(Q) = 0.65 mm.s(-)(1) (at pH 8.0). The signal intensity corresponded to the enzyme concentration assuming 1 Fe per mol active site. Upon addition of CO or cyanide to the enzyme, the isomer shift decreased to -0.03 mm.s(-)(1) and -0.00(1) mm.s(-)(1), and the quadrupole splitting increased to 1.38 mm.s(-)(1) and 1.75 mm.s(-)(1), respectively. The three spectra could be perfectly simulated assuming the presence of only one type of iron in Hmd. The low isomer shift is characteristic for Fe in a low oxidation state (0, +1, +2). When the spectra of the holoenzyme and of the CO- or cyanide-inhibited enzyme were measured at 4 K in a magnetic field of 4 and 7 T, the spectra obtained could be simulated assuming the presence of only the external magnetic field, which excludes that the iron in the active site of Hmd is Fe(I), high-spin Fe(0), or high-spin Fe(II). M?ssbauer spectra of the isolated Hmd cofactor are also reported.     

Lattice dynamics of KCN and NaCN in the disordered cubic phase

The rotational degrees of freedom of the CN^- dumbbell have been included in a shell model treatment of the lattice dynamics of KCN and NaCN. Recent experiments are discussed and compared with the model.