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We propose a new possibility to reconcile the coupling unification scenario with the triplet-doublet mass splitting based on a 5-dimensional supersymmetric model with SU (5) gauge symmetry. It is shown that the minimal supersymmetric standard model is derived on a 4-dimensional wall through compactification on S 1 /(Z2 × Z ′

Supersymmetric grand unified theories with nonuniversal soft supersymmetry-(SUSY-) breaking terms are studied. By integrating out the superheavy fields at a unification scale, we compute their low-energy effective Lagrangian. We find new contributions to the scalar potential specific to the nonuniversal supersymmetry breaking. A D-term contribution to the scalar masses is one example. The gauge hierarchy achieved by a fine-tuning in the superpotential would be violated in general due to the nonuniversal SUSY-breaking terms. We show, however, it is preserved for a certain class of the soft terms derived from a hidden ansatz. We also discuss some phenomenological implications of the nonuniversal supersymmetry breaking, including predictions of the radiative electroweak symmetry-breaking scenario and of no-scale-type models.PACS number(s): 12.10.Dm, 12.60.J~

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YddV from Escherichia coli (Ec) is a novel globin-coupled heme-based oxygen sensor protein displaying diguanylate cyclase activity in response to oxygen availability. In this study, we quantified the turnover numbers of the active [Fe(III), 0.066 min(-1); Fe(II)-O(2) and Fe(II)-CO, 0.022 min(-1)] [Fe(III), Fe(III)-protoporphyrin IX complex; Fe(II), Fe(II)-protoporphyrin IX complex] and inactive forms [Fe(II) and Fe(II)-NO, <0.01 min(-1)] of YddV for the first time. Our data indicate that the YddV reaction is the rate-determining step for two consecutive reactions coupled with phosphodiesterase Ec DOS activity on cyclic di-GMP (c-di-GMP) [turnover number of Ec DOS-Fe(II)-O(2), 61 min(-1)]. Thus, O(2) binding and the heme redox switch of YddV appear to be critical factors in the regulation of c-di-GMP homeostasis. The redox potential and autoxidation rate of heme of the isolated heme domain of YddV (YddV-heme) were determined to be -17 mV versus the standard hydrogen electrode and 0.0076 min(-1), respectively. The Fe(II) complexes of Y43A and Y43L mutant proteins (residues at the heme distal side of the isolated heme-bound globin domain of YddV) exhibited very low O(2) affinities, and thus, their Fe(II)-O(2) complexes were not detected on the spectra. The O(2) dissociation rate constant of the Y43W protein was >150 s(-1), which is significantly larger than that of the wild-type protein (22 s(-1)). The autoxidation rate constants of the Y43F and Y43W mutant proteins were 0.069 and 0.12 min(-1), respectively, which are also markedly higher than that of the wild-type protein. The resonance Raman frequencies representing ν(Fe-O(2)) (559 cm(-1)) of the Fe(II)-O(2) complex and ν(Fe-CO) (505 cm(-1)) of the Fe(II)-CO complex of Y43F differed from those (ν(Fe-O(2)), 565 cm(-1); ν(Fe-CO), 495 cm(-1)) of the wild-type protein, suggesting that Tyr43 forms hydrogen bonds with both O(2) and CO molecules. On the basis of the results, we suggest that Tyr43 located at the heme distal side is important for the O(2) recognition and stability of the Fe(II)-O(2) complex, because the hydroxyl group of the residue appears to interact electrostatically with the O(2) molecule bound to the Fe(II) complex in YddV. Our findings clearly support a role of Tyr in oxygen sensing, and thus modulation of overall conversion from GTP to pGpG via c-di-GMP catalyzed by YddV and Ec DOS, which may be applicable to other globin-coupled oxygen sensor enzymes.

We study the mass spectrum of superparticles within supersymmetric grand unified models. For gaugino masses, it is pointed out that the GUT-relation in the SU(5) model is applicable to a more general case where a grand-unified gauge group breaks down to the standard model gauge group by several steps. We also show that the mass spectrum of squarks and sleptons carries the information on the breaking pattern of the gauge symmetry. It is demonstrated in some SO(10) models how the scalar mass spectrum distinguishes various SO(10) breaking patterns from each other.

We study a gauge coupling unification scenario based on a nonsupersymmetric 5-dimensional model. Through an orbifold compactification, we obtain the Standard Model with split multiplets on a 4-dimensional wall, which is compatible with a grand unification.

We study the dynamical symmetry breaking in the gauge-Higgs unification of the five-dimensional theory compactified on an orbifold, S 1 /Z 2 . This theory identifies Wilson line degrees of freedom as ''Higgs doublets.'' We consider SU(3) c ϫSU(3) W and SU(6) models with the compactification scale of order of a few TeV. The gauge symmetries are reduced to SU(3) c ϫSU(2) L ϫU(1) Y and SU(3) c ϫSU(2) L ϫU(1) Y ϫU(1), respectively, through the orbifolding boundary conditions. We estimate the one loop effective potential of ''Higgs doublets,'' and find that the electroweak breaking is realized through the radiative corrections when there are suitable numbers of bulk fields possessing the suitable representations. The masses of ''Higgs doublets'' are O͑100͒ GeV in this scenario.