Photon polarization tensor and gauge dependence in three-dimensional quantum electrodynamics

Quantum electrodynamics in 2 + 1 dimensions, confinement, and the stability of U(1) spin liquids

Compact quantum electrodynamics in 2 + 1 dimensions often arises as an effective theory for a Mott insulator, with the Dirac fermions representing the low-energy spinons. An important and controversial issue in this context is whether a deconfinement transition takes place. We perform a renormalization group analysis to show that deconfinement occurs when N > Nc = 36/pi3 approximately to 1.161, where N is the number of fermion replica. For N < Nc, however, there are two stable fixed points separated by a line containing a unstable nontrivial fixed point: a fixed point corresponding to the scaling limit of the noncompact theory, and another one governing the scaling behavior of the compact theory. The string tension associated with the confining interspinon potential is shown to exhibit a universal jump as N --> Nc-. Our results imply the stability of a spin liquid at the physical value N = 2 for Mott insulators.

2'-Deoxynucleoside 5'-triphosphates modified at alpha-, beta- and gamma-phosphates as substrates for DNA polymerases

Replacement of alpha-, beta- and gamma-phosphate groups in 2'-deoxynucleoside 5'-triphosphates (dNTP) with phosphonate groups yields a new set of dNTP mimics with potential biological and therapeutic applications. Here, we describe the synthesis of 15 new dNTPs modified at alpha-, beta- and gamma-phosphates containing, in the case of dUTP, reporter and ligand groups at the C5 position of uracil. It was shown that gamma-substituted dNTPs were substrates for AMV reverse transcriptase despite of the large size of substituent at the gamma-phosphonate. On the other hand, these compounds were poorly utilized by DNA polymerase alpha. For dUTP analogues substituted at both gamma-phosphonate and C5 of uracil, the substrate affinity was 1-2 orders of magnitude lower than for their counterparts containing substituents either at gamma-phosphonate or C5 position. Meanwhile, C5-substituted beta, gamma-dibromomethylenediphosphonates demonstrated poor activity or were not active at all as substrates for AMV reverse transcriptase. Finally, 2'-deoxythymidine 5'-[beta, gamma-(methylphosphinyl)methylphosphonyl]-alpha-phosphate and its 3'-azido-3'-deoxy analog were substrates for AMV reverse transcriptase, but the substrate activity of these analogues was 50-100 times lower as compared with dTTP. HIV reverse transcriptase utilized these compounds 1 order of magnitude less efficiently than AMV reverse transcriptase; terminal deoxynucleotidyl transferase did not recognize them at all.