Silica, Alumina, and Clay-Catalyzed Alanine Peptide Bond Formation

The peptide bond formation of alanine (ala), ala + glycine (gly), ala + diglycine (gly₂), and ala + gly cyclic anhydride (cyc-gly₂) in drying/wetting cycles at 80°C was studied. Silica, alumina, and representative smectites—montmorillonite and hectorite—were used as catalysts, and the dependence of reaction yields on the available amount of water in the reaction systems was evaluated. Silica and alumina catalyze the formation of oligopeptide mainly in temperature fluctuation experiments, whereas higher amounts of water in the reaction system support clay-catalyzed reactions. Silica and alumina are much more efficient for amino acid dimerization than clays. Whereas only 0.1% of ala oligomerized on hectorite and no reaction proceeded on montmorillonite, about 0.9 and 3.8% alanine converted into its dimer and cyclic anhydride on silica and alumina, respectively. Clay minerals, on the other hand, seem to more efficiently catalyze peptide chain elongation than amino acid dimerization. The reaction yields of ala-gly-gly and gly-gly-ala from ala + gly₂ and ala + cyc-gly₂ reached about 0.3% on montmorillonite and 1.0% on hectorite. The possible mechanisms of these reactions and the relevance of the results for prebiotic chemistry are discussed. Received: 15 December 1996 / Accepted: 1 May 1997     

Skeletal troponin I as a marker of exercise-induced muscle damage

Sorichter, Stephan, Johannes Mair, Arnold Koller, WalterGebert, Daniel Rama, Charles Calzolari, Erika Artner-Dworzak, and BerndPuschendorf. Skeletal troponin I as a marker of exercise-inducedmuscle damage. J. Appl. Physiol.83(4): 1076-1082, 1997.The utility of skeletal troponin I (sTnI)as a plasma marker of skeletal muscle damage after exercise wascompared against creatine kinase (CK), myoglobin (Mb), and myosin heavychain (MHC) fragments. These markers were serially measured in normalphysical education teacher trainees after four different exerciseregimens: 20 min of level or downhill (16% decline) running(intensity: 70% maximal O₂uptake), high-force eccentric contractions (70 repetitions), orhigh-force isokinetic concentric contractions of the quadriceps group(40 repetitions). Eccentrically biased exercise (downhill running andeccentric contractions) promoted greater increases in all parameters.The highest plasma concentration were found after downhill running{median peaks: 309 U/l CK concentration ([CK])}, 466 µg/l Mb concentration([Mb]), 1,021 µU/l MHC concentration ([MHC]),and 27.3 µg/l sTnI concentration ([sTnI]). Level running produced a moderate response (median peaks: 178 U/l [CK],98 µg/l [Mb], 501 µU/l [MHC], and 6.6 µg/l [sTnI]), whereas the concentric contraction protocoldid not elicit significant changes in any of the markers assayed. sTnIincreased and peaked in parallel to CK and stayed elevated (>2.2µg/l) for at least 1-2 days after exercise. In contrast to MHC,sTnI is an initial, specific marker of exercise-induced muscle injury,which may be partly explained by their different intracellularcompartmentation with essentially no (MHC <0.1%) or a small solublepool (sTnI: median 3.4%).

     

A point mutation in the tyrosine hydroxylase gene associated with Segawa's syndrome

We have examined the molecular basis of Segawa's syndrome in six families with seven affected children. In one family two siblings with this disease carried a point mutation in exon 11 of the tyrosine hydroxylase gene, resulting in an amino acid exchange of Gln³⁸¹ to Lys³⁸¹. These results suggest that a change in tyrosine hydroxylase causes this form of Segawa's syndrome.     

Two polymorphic dinucleotide repeats in intron 44 of the dystrophin gene

Duchenne muscular dystrophy (DMD) is one of the most common and severe X-linked disorders with an incidence of approximately 1 in 3500 newborn males. In more than 60% of DMD patients, deletions of part or all of the dystrophin gene have been shown. Despite this, carrier detection still poses a problem in some cases, because of the enormous size of the gene and the lack of sufficient numbers of informative markers. Here, we report the isolation and characterization of two additional microsatellite markers (IVS44SK12 and IVS44SK21) in intron 44 of the dystrophin gene. Both markers are useful for carrier detection either by indirect DNA analysis or by direct proof of loss of heterozygosity.     

HPLC-analysis of algal pigments: comparison of columns,column properties and eluents

The effects of columns (Nucleosil C₁₈ODS, MZ-PAH, YMC-PACK C₃₀), column properties (inner diameters of 4 mm, 3 mm and 2 mm, pore-width 10 nm and 30 nm) and eluents (methanol, acetonitrile, acetone, water) were tested on the separation of algal pigments. The length of columns was 250 mm and particle size was 5 μm. Flow rates and gradients were adjusted to optimize peak separation; remaining chromatographic conditions were kept constant. The resolution of chromatographic systems was tested with pigment standards and various algal cultures. Total flow rate and retention times decreased with decreasing inner diameter, whereas pressure, sensitivity and peak-width increased. Pore width had negligible effects on the chromatographic separation of pigments under the test conditions. Only with acetonitrile as eluent were all the taxonomically important pigments resolved adequately: zeaxanthin (Cyanophyceae), lutein (Chlorophyceae), fucoxanthin (Bacillariopyceae), alloxanthin (Cryptophyceae), peridinin (Dinophyceae).     

Altered flower/fruit clusters of the kitul palm used as roosts by the short-nosed fruit bat, Cynopterus sphinx (Chiroptera: Pteropodidae)

The short-nosed fruit bat (Cynopterus sphinx) creates bell-shaped cavities in flower/fruit clusters of the kitul palm (Caryota urens) by chewing and severing flower and fruit strings. These cavities (stem tents) in which the bats roost are usually about one metre deep and 30 cm in diameter. We observed groups of bats roosting in fully-formed stem tents during the daytime, and the construction and subsequent occupancy of newly formed tent cavities. Stem tents are similar in principle to leaf tents except, instead of being formed when bats chew veins and the surrounding tissues of leaves, stem tents are formed in C. urens when bats completely cut several of the central flower/fruit strings. Flower/fruit strings are mostly severed when they are in an immature stage, at times when they are thin and widely spaced. Once these strings thicken and become heavily-laden with mature fruits, bats cannot penetrate the cluster to sever them. Our observations suggest that a single male enters an immature flower or fruit cluster either from below or the sides and severs the central strings along the peduncle. In early phases of stem-tent construction, C. sphinx severs flower/fruit strings at a rate of about one or two per day, and cluster alteration may continue upwards to two months. Only one immature flower/fruit cluster on a C. urens tree is available for alteration by bats at any given time. That this bat does not roost in the fruit/flower cluster during the day, when a tent is under construction, and the accumulation of chewed flower and fruit strings beneath such a cluster in the morning, suggests that tent construction by C. sphinx is a night-time activity.     

Feedback inhibition of sodium uptake in K+-depolarized toad urinary bladders

Ouabain-blocked toad urinary bladders were maintained in Na⁺-free mucosal solutions, and a depolarizing solution of high K⁺ activity containing only 5 mM Na⁺ on the serosal side. Exposure to mucosal sodium (20 mM activity) evoked a transient amiloride-blockable inward current, which decayed to near zero within one hour. The apical sodium conductance increased in the initial phase of the current decay and decreased in the second phase. The conductance decrease required Ca²⁺ to be present on the serosal side and was more rapid when the mucosal Na⁺ activity was higher. At 20 mM mucosal Na⁺ and 3 mM serosal Ca²⁺ the initial (maximal) rate of inhibition amounted to 20% in 10 min. The conductance decrease could be accelerated by raising the serosal Ca²⁺ activity to 10 mM. The inhibition reversed on lowering the serosal Ca²⁺ to 3 μM and, in addition, the mucosal Na⁺ to zero. Exposure of the mucosal surface to the ionophore nystatin abolished the Ca²⁺ sensitivity of the transcellular conductance, showing that the Ca²⁺-sensitive conductance resides in the apical membrane. The data imply that in the K⁺-depolarized epithelia, cellular Ca²⁺, taken up from the serosal medium by means of a Na⁺-Ca²⁺ antiport, cause feedback inhibition by blockage of apical Na⁺ channels. However, the rate of inhibition is small, such that this regulatory mechanism will have little effect at 1 mM serosal Ca²⁺ and less than 20 mM cellular Na⁺.     

Analysis of penicillin-binding sites with a micro method — The binding site of PBP 5 from Escherichia coli

Abstract A micro method for the isolation and characterization of the penicillin-binding sites in penicillin-binding proteins (PBPs) was developed. Only 10 nmol of a pure PBP are required for the whole procedure which is based on high-pressure liquid chromatography (HPLC). We showed that serine 44 in PBP 5 from Escherichia coli binds penicillin covalently.     

Thermophilic Bacilli growing with carbon monoxide

Four strains of obligately thermophilic Bacilli capable of growing with carbon monoxide as a sole carbon and energy source were isolated from settling ponds of a sugar factory. Most of them could be identified as strains of Bacillus schlegelii on the basis of cell wall composition, DNA homology menaquinone and DNA base content. Growth with CO was very fast (t _d =3 h) and was optimal at 65°C. No growth occurred below 50°C. As with the mesophilic carboxydotrophs, hydrogen plus carbon dioxide could also serve as autotrophic substrates. Growth of the isolates with CO depended on the presence of molybdenum in the growth medium. This suggested CO oxidase in the newly isolated Bacilli being a molybdenum hydroxylase similar to the enzymes from the mesophilic carboxydotrophs. Some data characterizing the CO-oxidizing activity in extracts of the thermophilic isolates are also provided.This paper is respectively dedicated to Professor Dr. H. G. Schlegel on the occasion of his 60th birthday     

The role of sodium-channel density in the natriferic response of the toad urinary bladder to an antidiuretic hormone

Summary Urinary bladders ofBufo marinus were depolarized, by raising the serosal K concentration, to facilitate voltage-clamping of the apical membrane. Passive Na transport across the apical membrane was then studied with near-instantaneous current-voltage curves obtained before and after eliciting a natriferic response with oxytocin. Fitting with the constant-field equation showed that the natriferic effect is accounted for by an increase in the apical Na permeability. It is accompanied by a small increase in cellular Na activity. Furthermore, fluctuation analysis of the amiloride-induced shot-noise component of the short-circuit current indicated that the permeability increase is not due to increased Na translocation through those Na channels which were already conducting prior to hormonal stimulation. Rather, the natriferic effects is found to be based on an increase in the population of transporting channels. It appears that, in response to the hormone, Na channels are rapidly recruited from a pool of electrically silent channels.