Proteomic analysis of the endoplasmic reticulum from developing and germinating seed of castor (Ricinus communis)

Endoplasmic reticulum (ER) has been prepared and analysed from germinating and developing castor bean endosperm. A combination of one- and two-dimensional (1-D and 2-D) gel electrophoresis was used to study the complexity of sample and protein differences between the two stages. The ER of the developing oilseed is central to the synthesis, sorting and storage of protein and lipid reserves while the germinating seed is concerned with their degradation. Sample complexity has been reduced by separation of ER proteins into lumenal, peripheral membrane and integral membrane subfractions. Membrane proteins pose specific problems in aggregation and binding to passive surfaces. We have overcome this by collection of membranes at density gradient interfaces and by silanization of plastic ware. Several major components have been identified from 1-D gels by N-terminal sequencing and matrix-assisted laser desorption/ionization (MALDI) peptide mass fingerprints. These include protein disulphide isomerase (PDI), calreticulin and developing-ER-specific oleate-12-hydroxylase involved in the biosynthesis of ricinoleic acid. In excess of 300 spots are detectable in each developmental fraction by high sensitivity 2-D gels. This is the first 2-D electrophoretic analysis of plant ER. These gels reveal significant differences between germinating and developing ER. Preparative loading 2-D gels of germinating ER have been run and 14 selected spots characterized by quadrupole time of flight tandem mass spectrometry (Q-TOF MS/MS). Ten of these proteins were assigned function on the basis of identity with existing castor database entries, or by homology with other species. Two proteins, aspartate proteinase precursor and N-carbamyl-L-aminohydrolase-like protein, appear to be absent from developing profiles. Most of the proteins identified are concerned with roles in protein processing and storage, and lipid metabolism which occur in the ER. Data from three of the assigned spots included unidentified peptides indicating the presence of more than one protein in these spots following 2-D electrophoresis. More extensive analysis will have to await developments in genomics but the basic separation technologies to simplify sample identity for a plant ER preparation have been established.     

Two-dimensional protein map of human vastus lateralis muscle

Protein samples of human vastus lateralis muscle were analyzed by two-dimensional gel electrophoresis, using immobilized pH gradients encompassing several pH regions in the first dimension and sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the second dimension. More than 500 protein spots on each gel were detected by silver staining, of which 150 were excised, digested in-gel with trypsin and characterized by matrix assisted laser desorptioin/ionization-mass spectrometry and tandem electrospray mass spectrometry. Using these techniques, 124 spots including contractile proteins and metabolic enzymes were identified. This database should provide a valuable resource for the definition of the functional properties of muscle fibres and for assessment of the influence of e.g., hypoxia, ischaemia and ageing on protein level.     

Radiation from an electric dipole in the presence of a corrugated cylinder

Summary A solution is outlined for the problem of an electric dipole which is located outside and parallel to the axis of a circular cylinder fo infinite length. The corrugated surface of the cylinder is assumed to be described by an anisotropic boundary impedance which specifies the ratios of the tangential electric and magnetic fields. It is shown that, in general, the radiated field is elliptically polarized.     

Induction by an oscillating magnetic dipole over a two layer ground

Summary An expression for the mutual electromagnetic coupling between two small loops over a two-layer ground is derived. The result is expressed in a form which is suitable for calculation by a digital computer. When the heights or separation of the loops are large compared to the skin depth in the ground, simple asymptotic formulas for the fields can de developed. The results are employed to obtain a convenient formula for the self-impedance of a loop over a two-layer ground.     

Impedance of an electric dipole located in a cylindrical cavity in a dissipative medium

The electromagnetic fields of an electric dipole located inside a cylindrical cavity or empty tunnel are formulated. The results are used to deduce an expression for the change of self-impedance due to the presence of the cavity or tunnel walls. A numerical evaluation of the resultant convergent integral and a summation of the angular harmonic series were performed. An important finding is that the input resistance of the dipole is approximately a constant for frequencies less than about 25 MHz for a typical tunnel radius of 2 m. Such results are shown to be in qualitative agreement with an earlier analysis of an electric dipole over a dissipative half-space.     

Induction in a conducting sheet by a small current-carrying loop

Summary The problem of a small current-carrying loop situated over a thin plane sheet of conducting material is solved. The cases are considered where the loop axis is oriented both perpendicular and parallel to the plane of the sheet.     

Transmission line theory for an insulated linear antenna in a fluid- or air-filled borehole

Using a transmission line theory, expressions for the propagation constant and characteristic impedance of a borehole antenna are derived. Both air-filled and fluid-filled holes are considered. The required modal equation is solved by a rapidly convergent iterative method. Some data for the input impedance and effective dipole moment for the terminated line are then provided. It appears that the presence of conducting fluid in the hole will not seriously impair the effectiveness of the radiating structure, but the voltage gradients in the insulation will be increased markedly.