Interactions of the amino acid residue at position 31 of the c-Ha-Ras protein with Raf-1 and RalGDS

The Ras and Rap1A proteins can bind to the Raf and RalGDS families. Ras and Rap1A have Glu and Lys, respectively, at position 31. In the present study, we analyzed the effects of mutating the Glu at position 31 of the c-Ha-Ras protein to Asp, Ala, Arg, and Lys on the interactions with Raf-1 and RalGDS. The Ras-binding domain (RBD) of Raf-1 binds the E31R and E31K Ras mutants less tightly than the wild-type, E31A, and E31D Ras proteins; the introduction of the positively charged Lys or Arg residue at position 31 specifically impairs the binding of Ras with the Raf-1 RBD. On the other hand, the ability of the oncogenic RasG12V protein to activate Raf-1 in HEK293 cells was only partially reduced by the E31R mutation but was drastically impaired by the E31K mutation. Correspondingly, RasG12V(E31K) as well as Rap1A, but not RasG12V(E31R), exhibited abnormally tight binding with the cysteine-rich domain of Raf-1. On the other hand, the E31A, E31R, and E31K mutations, but not the E31D mutation, enhanced the RalGDS RBD-binding activity of Ras, indicating that the negative charge at position 31 of Ras is particularly unfavorable to the interaction with the RalGDS RBD. RasG12V(E31K), RasG12V(E31A), and Rap1A stimulate the RalGDS action more efficiently than the wild-type Ras in the liposome reconstitution assay. All of these results clearly show that the sharp contrast between the characteristics of Ras and Rap1A, with respect to the interactions with Raf-1 and RalGDS, depends on their residues at position 31.     

Mechanical fatigue characteristics of Sn-3.5Ag-X (X=Bi, Cu, Zn and In) solder alloys

In our previous study, the fatigue life of Sn-3.5Ag-Bi alloy was found to be dominated by the fracture ductility of the alloy and to obey a modified Coffin-Manson’s law: (Δε_p/2D)· N _f ^α , where Δε_p is plastic strain range, N_f is fatigue life, and α and=C are nondimensional constants. In this study, copper, zinc, and indium are selected as the third element, and the effect of these elements on the isothermal fatigue properties of Sn-3.5%Ag alloy has been investigated. The relationship between fatigue life and crack propagation rate estimated from load drop curve during fatigue test is also discussed. The addition of copper, indium, and zinc up to 2% slightly decreases the fatigue life of Sn-3.5Ag alloy due to the loss of ductility, while the life still remains higher than that of tin-lead eutectic alloy. The modified Coffin-Manson’s equation can also be applied to ternary Sn-3.5Ag-X. It is found that both ductility and fatigue life are significantly responsible for the load drop rate of the alloy, which reflects the extent of crack propagation. The fatigue life of Sn-3.5Ag-X alloy is therefore dominated not by the kinds and amount of third element but by the ductility of each alloy.     

Three-dimensional visualization of pore structure in hardened cement paste by the gallium intrusion technique

It is widely known that the pore structure of concrete strongly influences its physical properties. Therefore, we developed a technique for the visualization of the pore structure because of clearing it correctly. However, this visualization is limited to two-dimensional imaging for sections of the specimen. As a result, in this study, we developed a technique for reconstructing the acquired 2D images of the pore structure into 3D form by stacking them. By using this image, the relationship between water permeability and pore connectivity was clarified, and it was shown clearly that the pore connectivity strongly affects the water permeability.     

Improving PDP picture quality by means of a motion-dependent equalizing-pulse technique

Abstract— When moving images are displayed on color plasma displays, motional artifacts such as dynamic false contours with disturbances of gray scales and colors are often observed. Reduction of the disturbances is essential to achieve PDPs with acceptable picture quality for TV use. The moving-picture quality can be improved to some extent by using an equalizing-pulse technique which augments or suppresses light-emission to compensate for the lack or surplus from the original signal. The disturbances, however, become significant as the speed of motion increases. In order to reduce the disturbances, the equalizing pulses are weighted according to the speed and direction of motion. The improvement can be enhanced further by combining the technique with a modified-binary-coded light-emission-period scheme. Disturbance is thus reduced by 82 dB. The technique is applicable to images moving at any speed in any direction. It can also be used for any pixel arrangement and any light-emission scheme.     

Effect of siloxane chain lengths of monomers on characteristics of pervaporation membranes prepared by plasma polymerization

Plasma-polymerized membranes were prepared from a series of monomers with the different siloxane chain lenghts, i. e., hexamethyldisiloxane, octamethyltrisiloxane, and decamethyltetrasiloxane, and effects of the starting monomers on both the structures of the plasma polymers and the pervaporation characteristics of ethanol/water mixture were investigated. By IR and XPS measurements, it was found that with increase of the siloxane chain lenghts of the monomer the siloxane chains in the plasma polymers were linked more continuously and smaller amounts of additional oxygen were newly incorporated into the polymers. All membranes obtained from the three monomers were found to be ethanol-permselective. From the standpoint of obtaining both high selectivity and high permeation rate, the monomer with the longer siloxane chain was profitable. The relations between the results of the analysis of the plasma polymers by IR and XPS measurements and the pervaporation characteristics obtained are discussed. © 1994 John Wiley & Sons, Inc.     

Contact of a spherical particle with a droplet

The collection of particles by liquid drops is profoundly influenced by the contact angle of the particles with the drops and the surface tension of the drops. The present investigation was undertaken to establish an equation with reference to the force which acts on a particle by surface tension after contact of a particle with a drop, and to simplify its solution. Moreover, the approximate equations obtained can be applied as regards the arbitrary contact angle of a particle with a drop and the arbitrary ratio of the radius of the drop to the particle. The agreement between theoretical and experimental values could be verified by this experiment.It is considered from these results that the approximate equations can be utilized when it is necessary to know the behaviour of a particle after contact with a liquid drop.     

Dyeing of silk cloth with colloidal gold

Silk cloth was dyed successfully by dipping it in a gold hydrosol which was prepared in the presence of a cationic surfactant, stearyltrimethylammonium chloride (SC). The color of thus dyed silk cloths is due to colloidal gold particles adsorbed on silk fibers and varies from reddish purple to dark purple according to the periods of dipping time and the amounts of SC in the gold hydrosol used. The mechanism for the adsorption of colloidal gold on the silk fibers is proposed.     

Effects of valence states of iron in iron phosphates on the catalytic activity in oxidative dehydrogenation of isobutyric acid

Oxidative dehydrogenation of isobutyric acid to methacrylic acid was studied over an iron phosphate catalyst with a P/Fe atomic ratio of 1.2. The freshly prepared catalyst consisting of Fe³⁺ is reduced with isobutyric acid to iron(II) pyrophosphate [Fe₂P₂O₇] via a bluish black intermediate. Under the reaction conditions, the fresh catalyst is reduced gradually to the intermediate and the Fe₂P₂O₇ is also reoxidized to the intermediate. However, both the catalytic activity and the selectivity were scarcely affected with a large variation in the valence states of iron in the bulk of iron phosphate. On the other hand, the studies on the reaction in the absence of oxygen revealed that the reaction is promoted by the redox cycle of iron phosphate.     

Effect of phosphorylation on activities of Rap1A to interact with Raf-1 and to suppress Ras-dependent Raf-1 activation

OBJECTIVE: To develop a method for the detection of bilateral Horner's syndrome in patients with bilateral interruption of the cervical sympathetic pathway or widespread autonomic neuropathy. METHODS: Darkness pupil diameters and redilatation times during light reflexes have been recorded with infrared TV pupillometry in 65 healthy subjects, 47 patients with unilateral Horner's syndrome, and 20 patients with bilateral Horner's syndrome. The aetiologies of the last group were diabetic autonomic neuropathy (three cases), amyloidosis (four), pure autonomic failure (PAF) (four), dopamine-beta-hydroxylase deficiency (two), and one case each of hereditary sensory and autonomic neuropathy (HSAN) type III, carcinomatous sympathetic neuropathy, familial dysautonomia, multiple system atrophy, Anderson-Fabry disease, and anterior spinal artery thrombosis at C5,6 and one had had bilateral cervical sympathectomies. RESULTS: Darkness diameters on the affected side were below normal in 12 patients with unilateral Horner's syndrome, the measurement yielding only 26% sensitivity for detection of the condition. By contrast, the time taken to reach three quarter recovery in the light reflex (T3/4) was abnormally prolonged (redilatation lag) in 33 of the same eyes. The measurement yielded 70% sensitivity and 95% specificity for detection of the condition. In 20 cases, diagnosed on clinical grounds as having bilateral Horner's syndrome of various aetiologies, pupil diameters were abnormally small on both sides in five and on one side in three patients. Fourteen of these patients had significant redilatation lag in both eyes, five patients in one eye, and one patient had it in neither eye. Measurement of redilatation lag was therefore a more sensitive diagnostic test than pupil diameter in both unilateral and bilateral Horner's syndrome. CONCLUSIONS: Provided that the pupils are not tonic, bilateral Horner's syndrome can be diagnosed on the basis of redilatation lag. It occurs clinically in some generalised autonomic neuropathies and with interruption of the local sympathetic nerve supplies to the two eyes.     

Tin pest in Sn-0.5 wt.% Cu lead-free solder

Tin pest (the product of the allotropic transformation of β-tin into α-tin at temperatures below 286 K) has been observed in a Sn-0.5 wt.% Cu solder alloy. Some 40 percent of the specimen surface was transformed into gray tin after aging at 255K for 1.5 years, and after 1.8 years, the proportion increased to about 70 percent. The degree of transformation in work-hardened areas is much higher than in other areas, suggesting residual stress might provide an additional driving force for the transformation into α-tin. The allotropic change results in a 26 percent increase in volume, and cracks are initiated to accommodate the changes in volume. Results indicate that tin pest could lead to total disintegration of micro-electronic solder joints. The tin-copper eutectic system may become a prominent lead-free solder, and tin pest could have major ramifications on service lifetime of electronic assemblies. For more information, contact Y. Kariya, The Open University, Materials Engineering Department, Walton Hall, Milton Keynes, MK7 6AA, United Kingdom; 011-44-1908-652-630; fax 011-44-1908-655-120; e-mail y.kariya@open.ac.uk.