Cloning and sequencing of 5' flanking sequence from the gene encoding 2S storage protein, from two Brassica species

Using oligodeoxyribonucleotide primers and the polymerase chain reaction, we have cloned and sequenced about 1.2 kb of upstream sequences from two members of the 2S seed storage protein-encoding gene family from Brassica juncea and B. oleracea. The two sequences bear more than 90% homology and have characteristic seed-specific promoter motifs. The high degree of sequence conservation indicates that this napin-encoding gene family evolved earlier than the divergence of the three primary Brassica species and their amphidiploids, and the sequences have been conserved due to some metabolic constraints in seed development.

Improved bacterial hosts for regulated expression of genes from lambda pL plasmid vectors

The construction and use of a set of Escherichia coli strains with defective lambda prophages that facilitate expression of genes cloned in lambda pL-plasmid vectors is described. These bacteria allow high and regulated expression of such genes, whereas a kanamycin-resistance marker (KmR) on the prophage allows easy identification and genetic transfer from strain to strain. Optimal conditions for examining gene expression with the pL-vector systems using these strains are discussed.

Shuttle cosmid vectors for the trypanosomatid parasite Leishmania

We have developed two shuttle cosmid vectors for the trypanosomatid protozoan parasite Leishmania. Cosmids cLHYG and cLNEO contain hyg and neo markers, conferring resistance to hygromycin B and G418, respectively, replicate extrachromosomally after transfection into promastigotes, and bear a unique BamHI cloning site. To ensure the representation of telomeric sequences, which represent about 5% of the Leishmania genome, random insert DNAs were prepared by shearing followed by blunt-end ligation with BamHI adapters. Representative genomic libraries from Leishmania species representing the four major pathogenic complexes were prepared using cosmid cLHYG. The cosmid libraries were efficiently transfected into Leishmania, and individual cosmids were readily recovered by transformation back into Escherichia coli. The relatively small size of the Leishmania genome (50 Mb) combined with the capacity and transfection efficiency of these cosmid libraries (> 1000 Leishmania transfectants/plate) suggests the feasibility of functional genetic complementation in this parasite.

Design of helix ends. Amino acid preferences, hydrogen bonding and electrostatic interactions

The amino acid sequence and chemical interactions at the ends of 163 helices were surveyed so as better to understand amino acid preferences previously observed [Richardson, J.S. & Richardson, D.C. (1988) Science 240, 1648-1652]. Amino acid preferences differed from the previous survey in some significant details and in ways that might affect the choice of amino acids during the design of a protein helix. The following major conclusions about helix ends were deduced from additional patterns of amino acid occurrence and interactions that were observed. (1) A specific pair of hydrogen bonds is often observed between a glutamic acid (or glutamine) side chain at the N3 position and the N-cap amide hydrogen, and between the N-cap side chain (often threonine) and the N3 amide hydrogen. This reciprocal interaction may be an important means of stabilizing the N-terminal end of a helix. (2) Negatively charged amino acids (aspartic acid and glutamic acid) at the N-terminal end of helices may be more important in stabilizing protein helices than positively charged residues (chiefly lysine) at the C-terminal end. (3) The identity of the residue at the N-cap position is correlated with the backbone conformation at that position. (4) Aspartic acid (or asparagine) at the N2 or N3 position may adopt a conformation that suggests a hydrogen-bonding interaction with the end of the helix, especially when the N-cap side chain does not form a hydrogen bond with the end of the helix.

Serotonergic-cholinergic neurotransmitters' function in brain during cadmium exposure in protein restricted rat

Daily subcutaneous injection of cadmium chloride (0.3 mg/100g bw) for two weeks to normal and protein restricted (5% casein) rats shows significant decrease in 5-HT concentration in cerebellum, medulla oblongata-pons, hypothalamus, striatum-hippocampus, midbrain-thalamus-subthalamus, and cortex in both dietary regimens. No significant change occurs in concentration of ACh in cerebellum, but there is a significant increase in cortex, whereas significant decrease occurs in rest of the discrete regions of brain in both dietary conditions. Results also indicate that the intensity of cadmium effect is more evident in discrete brain regions in protein restricted dietary condition than in the normal group. The inhibitory action of Cd on both neurotransmitters has been discussed.

Biophysical characterization of Vibrio El Tor typing phage e5

Vibrio cholerae typing phage e5, which can lyse only the El Tor strains of V. cholerae, was characterized. The phage had a polyhedral head 51 nm in diameter and a short tail 13 nm in length. It contained 13 structural polypeptides, with the molecular mass of the major component being 50 kDa. Phage chromosome comprised a 38.5-kb linear double-stranded DNA molecule with unique termini, as determined by restriction fragment analysis and electron microscopy, and had a G+C content of 35.5%. A physical map was constructed with the restriction endonucleases HaeII and HpaII. Adsorption of the phage to its host followed a biphasic kinetics and its intracellular growth was characterized by a latent period of 15 min and a burst size of 100 particles per infected cell. The phage was found to be moderately thermotolerant.

Rolling-circle replication of a high-copy BPV-1 plasmid

We investigated the replicating form of a bovine papillomavirus type 1 (BPV-1) deletion mutant by direct electron-microscopic analysis of low molecular weight cellular DNA fractions. The detection of viral plasmid DNA replication intermediates was facilitated by the isolation of a spontaneously transformed mouse cell subclone containing an unusually high viral genome copy number (approx. 1000 per cell), and by employing a slight modification of the Hirt fractionation procedure to reduce the level of contaminating linear chromosomal DNA fragments. We observed exclusively rolling-circle-type viral DNA replication intermediates, at a frequency of detection of approximately one replication intermediate per 200 monomeric circular viral DNA molecules. The demonstration of rolling-circles with longer-than-genome-length tails indicated that this high-copy viral plasmid was not subject to a strict once-per-cell-cycle mode of DNA replication. Our observations provide further evidence in favour of an alternative replication mode of the BPV-1 genome, and may help to explain earlier conflicting findings concerning the mechanism of stable BPV-1 plasmid copy-number-control.

Benzene Forms Hydrogen Bonds with Water

Fully rotationally resolved spectra of three isotopic species of 1:1 clusters of benzene with water (H(2)O, D(2)O, and HDO) were fit to yield moments of inertia that demonstrate unambiguously that water is positioned above the benzene plane in nearly free internal rotation with both hydrogen atoms pointing toward the pi cloud. Ab initio calculations (MP2 level of electron correlation and 6-31 G(**) basis set with basis set superposition error corrections) predict a binding energy D(e) greater, similar 1.78 kilocalories per mole. In both the experimental and theoretical structures, water is situated nearly 1 angstrom within the van der Waals contacts of the monomers, a clear manifestation of hydrogen bond formation in this simple model of aqueous-pi electron interactions.

Ganglio-N-tetraosylceramide (GA1) of bovine and human brain. Molecular characterization and presence in myelin

During our studies of bovine brain neutral glycosphingolipids (Ngsl's), we have purified a compound that co-migrates on thin-layer chromatogram with standard GA1 (purified by acid hydrolysis of GM1) and close to penta- (nLc5Cer) glycosylceramide from bovien erythrocytes. The structure of the purified Ngsl from brain has been established by permethylation and by stepwise exoglycosidase hydrolysis. 600 MHz 1H NMR spectroscopy of the oligosaccharide obtained from the Ngsl after endoglycoceramidase hydrolysis confirms the structure as ganglio-N-tetraosylceramide (GgOse4Cer or GA1) as Gal beta 1----3GalNAc beta 1----4Gal beta 1----4Glc beta 1----1Cer. We have identified GA1 in bovine, rat and human brain and myelin by TLC-immunostaining with monospecific anti-GA1 antiserum.

Hypertonic stress induces alpha B-crystallin expression

Alpha B-crystallin, a major lens protein, was induced in primary cultures of dog lens epithelial cells and glomerular endothelial cells when they were grown under conditions of hypertonic stress. With Western blot analysis using a specific alpha B-crystallin antibody, we observed a significant increase in the concentration of alpha B-crystallin protein in cells grown for 4-6 days in media supplemented with 150 mM NaCl or 250 mM cellobiose. These supplements increased the osmolarity of the medium from 300 to 550-600 mosmol kg-1. Alpha B-crystallin mRNA was also increased reaching a maximum four-fold increase in lens and 16-fold increase in kidney cells within 1-2 days. These studies demonstrate a type of regulation of alpha B-crystallin expression in cells from lenticular and non-lenticular tissues.

Guaranteed convergence in a class of Hopfield networks

A class of symmetric Hopfield networks with nonpositive synapses and zero threshold is analyzed in detail. It is shown that all stationary points have a one-to-one correspondence with the minimal vertex covers of certain undirected graphs, that the sequential Hopfield algorithm as applied to this class of networks converges in at most 2n steps (n being the number of neurons), and that the parallel Hopfield algorithm either converges in one step or enters a two-cycle in one step. The necessary and sufficient condition on the initial iterate for the parallel algorithm to converge in one step are given. A modified parallel algorithm which is guaranteed to converge in [3n/2] steps ([x] being the integer part of x) for an n-neuron network of this particular class is also given. By way of application, it is shown that this class naturally solves the vertex cover problem. Simulations confirm that the solution provided by this method is better than those provided by other known methods.

Direct visualization of plasmid DNA in bacterial cells

The direct visualization of plasmid DNA inside Escherichia coli cells is demonstrated using phase-fluorescence microscopy of DAPI (4',6-diamidino-2-phenylindole)-stained bacteria. Small as well as large plasmids could be detected, both in minicells and in cells of larger size. For large plasmids, even single molecules appeared to be within the detection limit. The fluorescence generated from monomers of small plasmids was probably below this limit, and for these plasmids the observed signals may represent aggregates. The distribution of the fluorescence foci might reflect specific plasmid positioning during partition and/or replication.

Characterization of 2S seed storage protein of Brassica campestris and its antigenic homology with seed proteins of other Cruciferae

The low molecular weight seed storage protein of Brassica campestris has been isolated and its amino acid composition determined. Antibody raised against this low molecular weight protein has been used to compare the antigenic similarity between the low molecular weight storage proteins of different Cruciferae seeds by immunoprecipitation and Western blotting. These studies revealed the existence of antigenically homologous proteins of identical molecular weights in seeds of other Cruciferae but absent in some other dicots like mung bean and tobacco seeds.

Herpes simplex virus type 1-specific cytotoxic T lymphocytes recognize immediate-early protein ICP27

The identity of herpes simplex virus type 1 (HSV-1) antigens that serve as targets for cytotoxic T lymphocytes (CTL) and their ability to induce protective immunity remain uncertain. In this article, we report the identification of the immediate-early protein ICP27 as a CTL antigen in H-2d mice but not in H-2k or H-2b mice. Calculation of the frequencies of H-2d-restricted virus-specific CTL demonstrated that approximately one-fourth of the total HSV-1-specific response was directed against ICP27. To define the location of this CTL epitope, four truncated derivatives of the ICP27 gene which place the epitope in a 217-amino-acid region (amino acids 189 to 406) near the central portion of the protein were constructed. Mice immunized with ICP27 were able both to induce HSV-1-specific CTL and to survive a lethal intraperitoneal challenge with virulent HSV-1. However, neither appreciable antibody nor delayed-type hypersensitivity responses were induced in immunized mice, and they were also unable to clear a local epithelial virus challenge. It appears that ICP27, although capable of inducing several aspects of the immune response, is by itself unable to provide complete immunity.

The Escherichia coli cell cycle: one cycle or multiple independent processes that are co-ordinated?

In the life cycle of a bacterium there are several key processes: cellular growth, chromosome replication and decatenation, nucleoid partition, septum formation, and cell division. These processes have to be carefully controlled and co-ordinated both with respect to each other and to the growth of the cell, and could be viewed as parts of a single cycle in which each step is dependent upon the previous one. Alternatively, they could be independently controlled and carefully tuned to each other without actually constituting a true cycle. In this review, using Escherichia coli as model system, we discuss these two ways of describing the bacterial life cycle. The evidence supporting independent control of the processes is presented, and some of the key questions in the elucidation of the regulation of the bacterial life cycle are discussed.

The E. coli cell cycle and the plasmid R1 replication cycle in the absence of the DnaA protein

In E. coli strain EC::71CW chromosome replication is under the control of the R1 miniplasmid pOU71. A dnaA850::Tn10 derivative of EC::71CW was viable, which confirmed that R1 can replicate in the absence of the DnaA protein. The frequency of initiation of replication was, however, lowered and cell division was severely disturbed due to underreplication of the chromosome. Both replication and cell division could be restored to normal by increasing the production of RepA, the rate-limiting protein for initiation of replication from the integrated R1 origin. Therefore, the RepA protein seems to compensate for the absence of DnaA in the initiation of replication and assembly of replisomes. The role of the DnaA protein in the initiation of DNA replication, and as an overall regulator of the chromosome replication and cell division cycles of E. coli, is discussed in view of these results.

A disialoganglioside of the globo-series from chicken skeletal muscle

We have isolated a disialoganglioside of the globo-series from chicken pectoral muscle. The compound was obtained by extraction followed by ion-exchange and silicic acid column chromatography and judged to be pure by thin-layer chromatography in three solvent systems. The structure of the ganglioside was determined by carbohydrate and ceramide composition analysis, sequential exoglycosidase digestion, methylation analysis, and 500-MHz 1H-NMR spectroscopy to be: (formula; see text) Analysis of the ceramide moiety indicated d18:1 sphingosine as the long-chain base, and C16:0, C18:0, C18:1, and C20:0 as the prevalent fatty acids. This glycolipid is only the second ganglioside of the globo-series, and the first disialo member of the series, found in chicken muscle.

Biogenic amines and ascorbic acid in rat brain following steroid contraceptive treatment

Chronic treatment with steroid contraceptive produced a decrease in dopamine and norepinephrine concentration in discrete brain areas and an increase in ascorbic acid level. We suggest that alteration in the level of biogenic amines by steroid contraceptive may have some functional correlation with the ascorbic acid concentration in rat brain.

Analysis of the bacterial cell cycle using strains in which chromosome replication is controlled by plasmid R1

As an alternative approach in the study of the Escherichia coli cell cycle, we have constructed strains in which chromosome replication is under the control of various plasmid R1 derivatives, IntR1 strains. The physiological properties of such strains are described. In intR1 strains, chromosome replication can be manipulated independently of cell-cycle-related control mechanisms, and the effects on cell division can be analysed. Using this approach, we have found that the timing of replication during the cell cycle is random in intR1 strains, that overreplication of the chromosome is lethal, and that chromosome replication does not trigger cell division. Current investigations include the study of the E. coli cell cycle in the absence of the DnaA protein, the effect on cell division of a specific inhibition of the initiation of chromosome replication, and the molecular basis of uni- and bidirectional replication.

In vivo effect of the tus mutation on cell division in an Escherichia coli strain where chromosome replication is under the control of plasmid R1

The phenotypic effect of the tus::kan mutation in an Escherichia coli strain, where the chromosome is replicated unidirectionally by an integrated R1 miniplasmid, was examined by flow cytometry and phase fluorescence microscopy. The tus+ cells exhibited perturbed cell division, as indicated by the presence of many elongated cells and filaments. Inactivation of the tus gene led to a reduction in the frequency of such elongated cells, presumably by eliminating Tus-mediated polar arrests of replication forks at ter sites, thereby shortening the time required for completion of chromosome replication.

Biosynthesis of GM1b and similar neolactoseries gangliosides by a partially purified chicken skeletal muscle sialyltransferase. Effect of sphingomyelin and acetylcholine

An alpha 2----3 glycolipid galactosyl sialyltransferase (SAT3/4) has been partially purified from embryonic chicken skeletal muscle. It is preserved in 50 mM Hepes buffer (pH 6.8) containing 1% Triton CF-54 and 20% glycerol at -70 degrees C for a period of 6 months without loss of activity. The SAT3+4 preparation transfers sialic acid to nLcOse4Cer, nLcOse6Cer and GgOse4Cer with respective Km values of 1.4, 0.83 and 0.45 mM. The activity is stimulated 2-3-fold at high substrate concentration and 6-8-fold at low substrate concentration; 0.01 and 0.005 mumol for asialo GM1 and 0.025 and 0.01 mumol for other glycolipids in the presence of phosphatidylcholine (PC) and sphingomyelin (SM) at an optimum concentration 0.75%. A higher concentration is inhibitory. SM from chicken muscle is more effective than that from bovine brain and the stimulation is qualitatively proportional to that of the saturated fatty acyl content of SM. Free fatty acids (palmitic and stearic), their sodium salts, other choline compounds including choline chloride, phosphorylcholine and acetylcholine either do not have any effect or are inhibitory. Acetylcholine, even in the presence of SM and PC, is strongly inhibitory (70%).

Ganglioside-modulated proteolysis by Ca2(+)-activated neutral proteinase (CANP): a role of glycoconjugates in CANP regulation

We examined ganglioside modulation of the activity of the millimolar Ca2(+)-sensitive form (mCANP) of calcium-activated neutral proteinase (CANP), which is enriched in myelin, from brain. GM1, GD1a, GT1a, GM2, and GM4 produced a concentration-dependent increase of mCANP activity. GD1a stimulated the greatest increase of enzyme activity (107%), followed by GT1a, whereas GD1b was inhibitory (56%). GM1, GM2, and GM4 stimulated but less so than GD1a and GT1a. Free N-acetylneuraminic acid, asialo-GM1, GM3, and a ganglioside mixture containing GM1, GD3, GD1a, and GD1b had no effect. The ganglioside-mediated modulation was not affected by trifluoperazine and chlorpromazine (phospholipid-binding antagonists). The mCANP Ca2+ requirement was significantly reduced in the presence of stimulatory gangliosides, and this increased sensitivity varied (10-50-fold) with ganglioside structure. Gangliosides may interact with membrane mCANP and modulate its proteolytic action.

Regulation of the calcium-activated neutral proteinase (CANP) of bovine brain by myelin lipids

Since calcium-activated neutral proteinase (CANP; calpain) activation occurs at the plasmalemma and the enzyme is found in myelin, we examined myelin lipid activation of brain CANP. Purified lipids were dried, sonicated and incubated with purified myelin CANP. The CANP was assayed using [14C]azocasein as substrate and the Ca2+ concentration ranged from 2 microM for muCANP to 5 mM for mCANP. Phosphatidylinositol (PI), phosphatidylserine (PS) and dioleoylglycerol stimulated the mCANP activity by 193, 89 and 78%, respectively. PI stimulated both m- and muCANP in a concentration-dependent manner, while phosphatidylcholine was least effective. Cerebroside and sulfatide at higher concentrations (750 microM) were stimulatory. The phospholipid (PL)-mediated activation was inhibited by the PL-binding drug trifluoperazine. PI reduced the Ca2+ requirement for CANPs significantly (20-fold). These results suggest that acidic lipids and particularly acidic phospholipids activate membrane CANP.

Two-dimensional spatial light modulators fabricated in Si/PLZT

We report in this paper the use of Si/PLZT technology in the fabrication of 2-D electrically and optically addressed spatial light modulators. First, a 12 x 12 electrically matrix addressed array was fabricated using simultaneous laser assisted diffusion and crystallization. Then, NMOS transistors exhibiting electron mobility of 550 cm(2)/V-s were fabricated in each unit cell of the matrix array and used to control the PLZT modulator. A dynamic range of 35:1 was achieved. A 16 x 16 optically addressed SLM array was also fabricated. In this case, to improve the optical sensitivity, a three-transistor CMOS detector-amplifier circuit was included in each unit cell of the array.

Management of a case of lagophthalmos by Gillies' method (a case report)

A case of facial palsy with lagophthalmos with exposure keratitis was corrected surgically by a method of temporalis transfer. When the slings were tightened leaving 1 cm gap in the palpebral aperture, lagophthalmos persisted. A secondary tightening procedure causing overlap of the upper lid over the lower yielded good results.

The predicted amino acid sequence of a centrosphere protein in dividing sea urchin eggs is similar to elongation factor (EF-1 alpha)

Monoclonal antibody (SU5), prepared from isolated mitotic spindles of sea urchin eggs, stained centrospheres preferentially and recognized a 50K (K = 10(3) Mr) polypeptide on immunoblots. Three positive clones were isolated by screening a lambda gt11 cDNA expression library prepared from sea urchin egg mRNA with SU5. One clone containing a 1.8-kb (1 kb = 10(3) base-pairs) insert was selected for further characterization. The beta-galactosidase fusion protein encoded by the cDNA clone had an apparent relative molecular mass of 150K, indicating that the inserted cDNA produced an estimated 34K of polypeptide. A single 2.2-kb RNA transcript was detected in sea urchin embryos using the cDNA clone as a probe. The cDNA fragment was sequenced and the nucleotide sequence was used to predict the amino acid sequence of the open reading frames in the clone. The putative gene product shows striking similarity to the peptide chain elongation factor (EF-1 alpha) from yeast, fungus, shrimp, insect, mouse and human.

Pediatric ocular trauma--a clinical presentation

A year long study of ocular injuries in children below the age of 15 years was conducted in the Ophthalmology Department of a general hospital. Fortyfour cases were studied. Of these 45.45% were in the age group of 6-10 years. The male to female ratio was 5.28 : 1. Pointed objects viz. sticks, wires etc. were found to be the common causative agents; the recent trend being of bow and arrow injuries. Ocular perforation was observed in 28 cases. On follow up of all the cases with ocular trauma, only 12 patients were found to have a visual acuity better than 6/18; perception of light was absent in 7 patients. A need for increased parental awareness and supervision of children is stressed upon.

Sialylation of lacto-N-neotetraosyl ceramide by a solubilized sialyltransferase(s) from chicken skeletal muscle: effect of phosphatidylcholine and sphingomyelin

The sialytransferase(s) that transfers sialic acid to lacto-N-neotetraosylceramide and other glycosphingolipids with a galactose nonreducing terminus has been successfully solubilized from embryonic chicken skeletal muscle. The enzyme can be stored in 50 mM HEPES (pH 6.8), 1% Triton CF-54, and 20% glycerol at -70 degrees C for as long as six months. Addition of phosphatidylcholine or sphingomyelin (0.167%) readily reactivates the stored inactive enzymes and such activity persists for about two weeks at 0 degrees-4 degrees C with the peak activity occurring at 1 to 2 days. Sphingomyelin from chicken muscle, which contains mainly C16:0 and C18:0, is 2.1-fold more effective than bovine brain sphingomyelin at the same concentration (0.4%).

Cytochrome c oxidase: evidence for interaction of water molecules with cytochrome a

The resonance Raman spectra of cytochrome c oxidase in protonated buffer compared to that in deuterated buffer indicate that water molecules are near the heme of cytochrome a. Differences in widths of the heme line at 1610 cm-1, after short exposure to D2O, and, additionally, of the heme line at 1625 cm-1, after long exposure, can be accounted for by changes in resonance vibrational energy transfer between modes of cytochrome a2+ and the bending mode of water molecules in the heme pocket. On the basis of the assignment of these modes, we place one water molecule near the vinyl group and one water molecule near the formyl group of the cytochrome a heme. These water molecules may play several possible functional roles.

Structural characterization of cytochrome c peroxidase by resonance Raman scattering

Resonance Raman scattering studies are reported on freshly prepared and aged ferric, ligand-free ferrous, and CO-bound ferrous cytochrome c peroxidase. The ferric form of the fresh enzyme has a heme which is penta-coordinate high spin, independent of buffer over the pH range 4.3-7, as determined by well established Raman marker lines. The aged enzyme displays a mixture of spin and coordination states, but it can be stabilized in the penta-coordinate high spin form in the presence of phosphate. These results can be accounted for by considering the size of the channel (6 A wide, 11 A long) between the distal side of the heme and the outer surface of the protein. A phosphate ion may be accommodated in this channel resulting in the stabilization of the distal heme pocket. The ferrous cytochrome c peroxidase in both the ligand-free and CO-bound states has an acidic and an alkaline form. The acidic form has the characteristic spectral features of peroxidases: a high frequency iron-histidine stretching mode (248 cm-1), a high frequency Fe-CO stretching mode (537 cm-1), and a low frequency C-O stretching mode (1922 cm-1). At alkaline pH these frequencies become similar to those of hemoglobin and myoglobin, with the corresponding modes located at 227, 510, and 1948 cm-1, respectively. We attribute the acid/alkaline transition in the ferrous forms of cytochrome c peroxidase to a rearrangement mainly of the proximal side of the heme, culminating in a change of steric interactions between the proximal histidine and the heme or of the hydrogen bonding network involving the proximal histidine. The new data presented here reconcile many inconsistencies reported in the past.

The role of water near cytochrome a in cytochrome c oxidase

Resonance Raman scattering studies of cytochrome c oxidase reveal that two vibrational modes narrow upon placing the enzyme in D2O. This is interpreted as evidence for the presence of water molecules near cytochrome a that increase the linewidth of the heme modes due to resonance vibrational energy transfer to the H2O bending mode. From the nature of the modes in which the broadening is detected, it is deduced that the water molecules are located near the formyl and the vinyl substituents of the cytochrome a. The change in width in the formyl mode appears quickly, whereas that in the vinyl mode only develops after extended exposure of the enzyme to D2O. On the basis of these results we propose a new mechanism for proton translocation. In this hypothesis water molecules at the active site become activated and are dissociated into protons and hydroxyl groups due to changes in the pKas of residues near the heme when the redox state of the cytochrome a changes. Structural features of the protein stabilize this charge separation and allow directional migration of protons to the cytosolic side of the inner mitochondrial membrane. It is pointed out that this mechanism may be operative in all proton-translocation complexes, and it is observed that in bacteriorhodopsin, also a proton pump, water molecules are detected near the active site lending support to the generality of this mechanism.

Selective devascularisation of stomach and lienopulmopexy for prevention of bleedings in portal hypertension in children

Dissatisfied with different operative procedures for prevention of recurrent bleedings in childhood portal hypertension, many surgeons nowadays treat their patients conservatively during episodic attacks and advocate one of the shunt procedures in adolescence when the splenic vein becomes sufficiently widened (more than 1 cm). Even then mortality cannot be avoided in some bad risk patients especially those living in remote villages lacking facilities for blood transfusion and high speed transport service. In this situation thoracic transposition of spleen and lienopulmopexy was advocated by Nylander and Turumen, Auvert, M. Bettex and others. We prefer a further simpler procedure and perform selective devascularisation of stomach and lienopulmopexy. It allows rapid development of collaterals between splenic pulps on the portal side and subpleural venous plexus on the systemic side to achieve effective gastric devascularisation to prevent further bleeding without hindering the existing portal flow through the liver to avoid the possible occurrence of encephalopathy. Of 21 operated cases one died on the 5th postoperative day and the remaining 20 are doing well. 1/2-5 1/2 years' follow-up revealed negligible morbidity and no recurrence of bleeding in any of them. Both procedures work on the same principle.

Transcriptional activation of ColE1 DNA synthesis by displacement of the nontranscribed strand

Plasmid ColE1 can replicate using RNAase H and DNA polymerase I. However, it can also replicate in the absence of these enzymes. In this case, formation of a persistent hybrid between a transcript (RNA II) and the DNA indirectly activates subsequent DNA synthesis, instead of providing a primer as it does in the presence of these enzymes. To activate DNA synthesis, a certain length is required for the hybridized region and the region of minimum length cannot include a palindrome. These results show that the single-stranded region of DNA displaced by the hybridization is responsible for the activation. A single-stranded region was identified on the nontranscribed strand by its enhanced reactivity to dimethyl sulfate. The necessary length for the single-stranded region is at least 40 nucleotides. The region probably provides a site for initial binding of a helicase that further unwinds the template DNA for initiation of DNA synthesis.

Multiple mechanisms for initiation of ColE1 DNA replication: DNA synthesis in the presence and absence of ribonuclease H

A transcript (RNA II) of plasmid ColE1 that hybridizes with the template DNA is cleaved by RNAase H and used as a primer by DNA polymerase I. However, the plasmid can replicate in bacteria lacking both enzymes, apparently using a different mechanism of initiation of replication. Here we report in vivo and in vitro studies on initiation of DNA replication in the presence or absence of either or both enzymes. Hybridization of RNA II with the template DNA is always required for initiation. Hybridized RNA II is cleaved by RNAase H to form a primer or used as a primer without cleavage by RNAase H. Hybridization also creates a single-stranded region on the nontranscribed strand that can serve as a template for synthesis of the lagging strand in a reaction that does not require DNA polymerase I. Lagging strand synthesis terminates 17 nucleotides upstream of the normal replication origin, forcing unidirectional replication.

Chloroplast as a Locale of L-myo-Inositol-1-Phosphate Synthase

Chloroplasts from 5 to 7 day old Vigna radiata seedling, grown under alternate light/dark conditions or from green Euglena gracilis Z. cells have been found to harbor L-myo-inositol-1-phosphate synthase (EC 5.5.1.4) activity. In contrast, dark-grown V. radiata seedlings, or streptomycin-bleached Euglena cells exhibit either reduced or no enzyme activity. An apparent enhancement of the chloroplastic inositol synthase by growth in presence of light is observed.

Cryogenic stabilization of myoglobin photoproducts

The low frequency resonance Raman spectra of photodissociated carbon monoxymyoglobin at cryogenic temperatures (4-77 K) differ from those of deoxymyoglobin. Intensity differences occur in several low frequency porphyrin modes, and intensity and frequency differences occur in the iron-histidine stretching mode. This mode appears at about 225 cm-1 in deoxymyoglobin. At the lowest temperature studied, approximately 4 K, the frequency of the iron-histidine stretching mode in the photoproduct is approximately 233 cm-1, and the intensity is very low. When the temperature of the photoproduct is increased, the intensity of the mode increases, but its frequency is unchanged. The differences between the photoproduct and the deoxy preparation persist to 77 K, the highest temperature studied, and are independent of whether samples are frozen in phosphate buffer or a 50:50 ethylene glycol/phosphate buffer mixture. It is proposed that the frequency of the iron-histidine stretching mode is governed by the tilt angle of the histidine with respect to the normal to the heme plane, and the intensity of the mode is governed by the overlap between the sigma orbital of the iron-histidine bond and the pi orbital of the porphyrin macrocycle. This model can account for differences between the resonance Raman spectra of the photoproduct and the deoxy preparations of both hemoglobin and myoglobin. Furthermore, by considering the F-helix motions in going from 6-coordinate to 5-coordinate hemoglobin and myoglobin, the heme relaxation of these proteins at room temperature with 10-ns pulses can be explained. Based on the findings reported here, low temperature relaxation pathways for both hemoglobin and myoglobin are proposed.

Resonance Raman characterization of the 7-ns photoproduct of (carbonmonoxy)hemoglobin: implications for hemoglobin dynamics

Resonance Raman spectra are reported for deoxyhemoglobin (deoxyHb) and the (carbonmonoxy)hemoglobin (HbCO) photoproduct Hb by use of 7-ns YAG laser pulses at wavelengths of 416 and 532 nm, where enhancement is observed for totally symmetric and nontotally symmetric modes, respectively. The frequencies of the porphyrin skeletal modes v10, v2, v19, v11, and v3 have been determined to be 1602, 1559, 1553, 1542, and 1466 cm-1 in Hb. These frequencies are 2-3 cm-1 lower than the corresponding frequencies for deoxyHb. The v19 and v11 frequencies are at the expected values for a Ct-N distance of 2.057 A, the known core size for a 6-coordinate high-spin FeII-porphyrin complex. The remaining frequencies, however, deviate from the core size correlations for these modes in the same direction as do those of deoxyHb, suggesting that the porphyrin ring is domed in both species. Thus, the heme structure is similar for deoxyHb and Hb but is slightly expanded in the latter. The expanded heme in Hb implies a restraint on the full out-of-plane displacement of the Fe atom, by an estimated approximately 0.1 A relative to deoxyHb. This could result from a residual interaction with the CO molecule if the latter remains held by the protein against the Fe atom, in a high-spin 6-coordinate complex. The available spectroscopic evidence suggests that such a complex may be stabilized at 4 K but is unlikely to persist at room temperature beyond the electronic relaxation (0.35 ps) of the electronically excited heme.(ABSTRACT TRUNCATED AT 250 WORDS)

A simple procedure for the preparation of pure kinetoplast DNA network free of nuclear DNA from the kinetoplast hemoflagellate Leishmania donovani

A simple, inexpensive procedure for preparing pure kinetoplast DNA network from Leishmania donovani is described. L. donovani promastigotes were lysed by incubating with pronase in presence of sodium dodecylsulfate. Crude kinetoplast DNA networks were obtained by centrifugation of the lysate through a 20% sucrose solution. The pellet containing kinetoplast DNA was deproteinized by phenol extraction. Contaminating nuclear DNAs were removed by denaturation with alkali, neutralization, and addition of polyethylene glycol-8000 to a concentration of 10% to facilitate precipitation of kinetoplast DNA. kDNA isolated after centrifugation was deproteinized several times with phenol and finally precipitated with ethanol. The average yield by this procedure is 30-50 micrograms of kDNA per gram of wet cells. By slot-blot hybridization with a nuclear DNA probe, no nuclear DNA contamination of the kDNA networks could be detected.