B-Cyclin/CDKs Regulate Mitotic Spindle Assembly by Phosphorylating Kinesins-5 in Budding Yeast

Although it has been known for many years that B-cyclin/CDK complexes regulate the assembly of the mitotic spindle and entry into mitosis, the full complement of relevant CDK targets has not been identified. It has previously been shown in a variety of model systems that B-type cyclin/CDK complexes, kinesin-5 motors, and the SCFCdc4 ubiquitin ligase are required for the separation of spindle poles and assembly of a bipolar spindle. It has been suggested that, in budding yeast, B-type cyclin/CDK (Clb/Cdc28) complexes promote spindle pole separation by inhibiting the degradation of the kinesins-5 Kip1 and Cin8 by the anaphase-promoting complex (APCCdh1). We have determined, however, that the Kip1 and Cin8 proteins are present at wild-type levels in the absence of Clb/Cdc28 kinase activity. Here, we show that Kip1 and Cin8 are in vitro targets of Clb2/Cdc28 and that the mutation of conserved CDK phosphorylation sites on Kip1 inhibits spindle pole separation without affecting the protein's in vivo localization or abundance. Mass spectrometry analysis confirms that two CDK sites in the tail domain of Kip1 are phosphorylated in vivo. In addition, we have determined that Sic1, a Clb/Cdc28-specific inhibitor, is the SCFCdc4 target that inhibits spindle pole separation in cells lacking functional Cdc4. Based on these findings, we propose that Clb/Cdc28 drives spindle pole separation by direct phosphorylation of kinesin-5 motors

PROPERTIES OF ALXGA1-XAS WITH AN ALAS BUFFER LAYER ON SI SUBSTRATES GROWN BY METALORGANIC VAPOR-PHASE EPITAXY

We present the details of growth by metalorganic vapor phase epitaxy and characterization of undoped and Sn doped Al(x)Ga(1-x)As (0 lesser-than-or-equal-to x lesser-than-or-equal-to 0.3) on Si substrates with AlAs buffer layer. Double X-ray diffraction has been performed on these samples and the estimated dislocation density is in the order of 8 x 10(6) cm-2. The carrier concentration in these samples were obtained by Schubnikov-De Haas effect and the observed oscillations compare very well with the Al(x)Ga(1-x)As grown on GaAs substrates. The photoluminescence efficiency in the Sn-doped Al(x)Ga(1-x)As/Si sample is about 640 times greater than in the undoped one and this is attributed to annihilation of non-radiative centers by Sn atoms. The biaxial stress in these films is estimated from the peak positions in the photoluminescence spectra measured as a function of temperature.1084173261562

Properties Of Alxga1-xas With An Alas Buffer Layer On Si Substrates Grown By Metalorganic Vapor Phase Epitaxy

We present the details of growth by metalorganic vapor phase epitaxy and characterization of undoped and Sn doped AlxGa1-xAs (0≤ x ≤ 0.3) on Si substrates with AlAs buffer layer. Double X-ray diffraction has been performed on these samples and the estimated dislocation density is in the order of 8x106 cm-2. The carrier concentration in these samples were obtained by Schubnikov-De Haas effect and the observed oscillations compare very well with the AlxGa1-xAs grown on GaAs substrates. The photoluminescence efficiency in the Sn-doped AlxGa1-xAs/Si sample is about 640 times greater than in the undoped one and this is attributed to annihilation of non-radiative centers by Sn atoms. The biaxial stress in these films is estimated from the peak positions in the photoluminescence spectra measured as a function of temperature. © 1991.1083-4615620Fan, Phillips, Tsaur, Heteroepitaxy on Silicon (1987) Mater. Res. Soc. Symp. Proc., 91. , Mater. Res. Soc, Pittsburgh, PAAkyiama, Kawarada, Kaminishi, Growth of GaAs on Si by MOVCD (1984) Journal of Crystal Growth, 68, p. 21Fisher, Masselink, Klein, Henderson, McClinn, Klein, Morkoc, Wasburn, (1984) J. Appl. Phys., 58, p. 344Wang, (1984) Appl. Phys. Letters, 44, p. 1149Tsaur, Metze, (1984) Appl. Phys. Letters, 45, p. 535Basmaji, Li, Hipolito, Allan, Lavielle, Portal, Proc. 4th Brazillian School of Semi-conductors Physics (1989) Proc. 4th Brazillian School of Semi-conductors Physics, , Belo Horizonte, to be publishedGay, Hirsch, Kelley, The estimation of dislocation densities in metals from X-ray data (1953) Acta Metallurgica, 1, p. 315Sheldon, Yacobi, Jones, Dunlavy, (1985) J. Appl. Phys., 58, p. 4186Soga, Hahoi, Sakai, Takayasu, Umeno, (1984) Electron. Letters, 20, p. 916Aspnes, (1980) Handbook of Semiconductors, 2, p. 109. , T.S. Moss, North-Holland, AmsterdamZemon, Shastry, Norris, Jagganath, Lambert, (1986) Solid State Commun., 58, p. 457Kuo, Vong, Cohen, Stringfellow, (1985) J. Appl. Phys., 57, p. 5428Soga, Hattori, Sakai, Umeno, (1986) J. Crystal Growth, 77, p. 49

PHOTOREFLECTANCE MEASUREMENTS ON SI DELTA-DOPED GAAS SAMPLES GROWN BY MOLECULAR-BEAM EPITAXY

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CONTINUOUS TO BOUND INTERBAND-TRANSITIONS IN DELTA-DOPED GAAS-LAYERS

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Continuous To Bound Interband Transitions In δ-doped Gaas Layers

We have studied the interband transitions of several silicon δ-doped GaAs samples using the technique of photoreflectance spectroscopy. The features observed in the optical spectra above the GaAs fundamental energy gap are tentatively attributed to transitions involving continuous valence band states and quantum-confined states at the conduction-band. The observed interband transition energies are in qualitative agreement with the self-consistently calculated ones taking into account the spreading of dopants. © 1990.82205208Bottka, Gaskill, Sillmon, Henry, Glosser, (1988) J. Electron. Mater., 17, p. 161Glembocki, Bottka, Furneaux, (1985) J. Appl. Phys., 57, p. 432Glembocki, Shanabrook, Bottka, Beard, Comas, (1985) Appl. Phys. Lett., 46, p. 970Shen, Pan, Pollak, Dutta, AuCoin, (1987) Phys. Rev., 36 B, p. 9384Bernussi, Iikawa, Motisuke, Basmaji, Li, Hipolito, (1990) J. Appl. Phys., 67, p. 4149(1990) Proc. Soc. of Photo-Opt. Instrum. Eng., , and also, to be publishedSnow, Glembocki, Shanabrook, (1988) Phys. Rev., 38 B, p. 12483Aspnes, (1980) Handbook on Semiconductors, 2, p. 109. , T.S. Moss, North Holland, Amsterda

ATOMIC-FORCE MICROSCOPY STUDIES ON VARIOUS TYPES OF PHOTOLUMINESCENT POROUS SILICON

The structural characteristics of anodically-etched porous silicon (PS) layers emitting at different energy levels and with various luminescence fatigue strengths, recently classified into types A, B and C are compared using atomic force microscopy. Quantum-size micro-particles have been observed in type A PS within amorphouslike contrast, but only fairly rough amorphous grain-like structures have been observed in type B and C PS. Drastic quenching of photoluminescence in the PS layer after deposition of a capping layer of amorphous silicon is also reported.9430330