Cavity design for high-frequency axion dark matter detectors.

In an effort to extend the usefulness of microwave cavity detectors to higher axion masses, above ∼8 µeV (∼2 GHz), a numerical trade study of cavities was conducted to investigate the merit of using variable periodic post arrays and regulating vane designs for higher-frequency searches. The results show that both designs could be used to develop resonant cavities for high-mass axion searches. Multiple configurations of both methods obtained the scanning sensitivity equivalent to approximately 4 coherently coupled cavities with a single tuning rod.

Expression of the nuclear gene encoding mitochondrial ATP synthase subunit alpha in early development of Drosophila and sea urchin.

Complementary DNAs encoding nuclear-coded mitochondrial ATP synthase subunit alpha of Drosophila melanogaster and Strongylocentrotus purpuratus were obtained by a combination of library screening and redundant PCR. The entire coding sequence of the precursor polypeptide was inferred for both species. Southern blots to genomic DNA indicated that the gene is almost certainly single-copy in both organisms. Northern blots to RNA from staged developmental series showed that ATP synthase subunit alpha mRNA is represented in the egg, declines in abundance during cleavage, and is replenished by zygotic transcription in both species. However, the extent and timing of these changes differ significantly in the two species studied. Nuclear-coded and mitochondrially encoded ATP synthase genes appear to be temporally co-regulated in Drosophila, but not sea urchin development.

The myosin-bound form of protein phosphatase 1 (PP-1M) is the enzyme that dephosphorylates native myosin in skeletal and cardiac muscles.

The myosin-bound form of protein phosphatase 1 (PP-1M) and the glycogen-bound form (PP-1G) together account for virtually all the phosphatase activity in rabbit skeletal muscle extracts towards native myosin. PP-1M has a 3-fold higher activity towards native myosin than does PP-1G and accounts for at least 60% of the myosin phosphatase activity in rabbit skeletal muscle. PP-1M accounts for 90% of the myosin phosphatase activity in bovine cardiac muscle, where PP-1G is essentially absent. The high activity of PP-1M towards native myosin appears to arise from interaction of the catalytic subunit with the putative myosin-binding subunit, since chymotryptic digestion liberates a catalytic subunit having the same characteristics as that released by limited proteolysis of PP-1G. Protein phosphatase 2A in skeletal and cardiac muscles is very active towards the isolated myosin P-light chain, but ineffective in dephosphorylating native myosin. The results suggest that PP-1M is the enzyme that dephosphorylates myosin in skeletal and cardiac muscle.

Identification of a third form of protein phosphatase 1 in rabbit skeletal muscle that is associated with myosin.

A third form of protein phosphatase 1 has been identified in skeletal muscle which is distinct from the species composed of the catalytic subunit complexed to the glycogen-binding subunit (protein phosphatase 1G) or inhibitor-2 (protein phosphatase 1I). The third form has an apparent molecular mass of 110 kDa, is not immunoprecipitated by antibody prepared against the glycogen-binding subunit, does not interact with glycogen and is devoid of inhibitor-2. It is tightly bound to myosin and is therefore termed protein phosphatase 1M.

Identification of the sites on rabbit skeletal muscle protein phosphatase inhibitor-2 phosphorylated by casein kinase-II.

Inhibitor-2 was phosphorylated by casein kinase-II in vitro at a rate similar to that of glycogen synthase, a physiological substrate of this protein kinase. The major phosphorylation sites were identified as serines-86, -120 and -121, the peptide containing serines-120 and -121 being labelled about 2.5-fold more rapidly than that containing serine-86. The 13 residues C-terminal to serine-121 (SGEEDSDLSPEERE) contain seven acidic amino acids, while the six residues following serine-86 (SDTETTE) contain three. These results are consistent with the known specificity requirements of casein kinase-II. The three serines are C-terminal to the threonine (residue 72) whose phosphorylation by glycogen synthase kinase-3 is potentiated by prior phosphorylation with casein kinase-II. This reinforces the view that a C-terminal phosphoserine residue is important for the specificity of glycogen synthase kinase-3. Identification of the residues phosphorylated by casein kinase-II will facilitate further studies on the in vivo phosphorylation state of inhibitor-2.

Molecular mass of inhibitor-2 from rabbit liver.

Inhibitor-2 was partially purified from rabbit liver by fractionation with ammonium sulphate, heat treatment at 100 degrees C, precipitation with trichloroacetic acid, chromatography on DEAE-cellulose at pH 8.5 and 5.0 and gel filtration on Sephadex G-100 (Stokes radius, 3.4 nm). The protein behaved as a single component at each step and migrated on SDS-polyacrylamide gels as a 31 kDa protein. Its properties were indistinguishable from those of skeletal muscle inhibitor-2. The results disagree with the report of Khandelwal and Zinman (J. Biol. Chem. (1978) 253, 560-565) that hepatic inhibitor-2 is a 14 kDa protein.