1H, 13C and 15N backbone and side chain resonance assignments of a 28 kDa active mutant of maize ribosome-inactivating protein (MOD)

We report the full resonance assignments of MOD, which is an active mutant of maize ribosome-inactivating protein (mRIP). mRIP is a unique RIP which is synthesized as an inactive precursor and processed by removal of an internal inactivation region to yield an active form.     

Coupling of DNA replication and cell division: sulB is an allele of ftsZ.

Treatments that damage DNA in Escherichia coli result in the inhibition of cell division. This inhibition is controlled by the lexA-recA regulatory circuit and can be specifically uncoupled by the mutations sulA (sfiA) and sulB (sfiB), which map at 21 and 2 min, respectively. Presently it is thought that sulA codes for an inducible inhibitor of cell division, the expression of which is controlled directly by the lexA repressor. In this report, it is shown that sulB is an allele of ftsZ, an essential cell division gene. A sulB mutation leads to an altered ftsZ gene product which is slightly thermosensitive and has an altered mobility on polyacrylamide gels. It is suggested that the altered ftsZ gene product is resistant to the sulA inhibitor, thus permitting cell division after induction of the SOS response. It is also shown that an increase in the gene dosage of ftsZ delays the onset of filamentation after SOS induction.     

Biological properties of two models of calcitonin gene related peptide with idealized amphiphilic alpha-helices of different lengths

Previous studies on calcitonin gene related peptide (CGRP) have demonstrated that it has the characteristics of an amphiphilic peptide, and from an examination of the sequence, we have proposed that it contains an amphiphilic alpha-helix. We have synthesized two analogues of CGRP which have different lengths of idealized amphiphilic alpha-helical secondary structure. The first model, CGRM-1, has been substituted with residues generating an idealized amphiphilic alpha-helix in the region between residues 8 and 25, equivalent to approximately five turns of an alpha-helix. This peptide is not an agonist in any of our bioassays, but it does bind with low affinity to rCGRP receptors in crude liver membranes. Our second model, CGRM-2, has an idealized amphiphilic alpha-helix between residues 8 and 18, which is equivalent to approximately three turns of an alpha-helix. In an in vitro rat vas deferens assay, this peptide is an agonist with a potency one-fourth that of the native hormone. However, the potency of CGRM-2 in an adenylate cyclase assay is much lower, only 1/140th the potency of CGRP. Both model peptides display amphiphilic characteristics commensurate with their design. We conclude that there is an amphiphilic alpha-helix in rCGRP between residues 8 and 18 and that this helix terminates in the vicinity of residue 18.     

Progressive chorioretinal degeneration in a female carrier of the choroideremia gene: A case report

Choroideremia is a generalized hereditary degeneration following an X-linked recessive trait. Its pathogenesis is related to an early atrophy of the choroidal circulation at the choriocapillaris and at the retinal pigment epithelium. Because it is inherited as an X-linked trait, it affects males most severely with female carriers generally being relatively asymptomatic. A report of an extremely rare case of a presumed female carrier with male-like visual symptoms and clinical signs is presented. In addition to a discussion of this atypical case of a female carrier with progressive degeneration, an overview of the disease is presented, including clinical features, pathophysiology, differential diagnoses and management.     

An analysis of extended and exponentially-fed-batch cultures.

Under certain conditions it is shown that an extended culture is equivalent to an exponentially-fed-batch culture, that an exponentially-fed-batch culture (and an extended culture) can be maintained at a steady state and that an exponentially-fed-batch culture may be mimicked by a continuous-flow culture with a constant dilution rate. Operational conditions required to maintain steady states are specified.     

Truncus arteriosus: an autosomal recessive disease?

Truncus arteriosus is an uncommon heart malformation; it is not reported that recurrence is high; nevertheless authors report three families with two or more cases; in the third there is a very high consanguinity (two uncle-niece marriages). The authors compare the situation with hypoplastic left heart and think that some cases of truncus arteriosus would have an autosomal recessive inheritance. That is an another argument for suggesting an echocardiographic survey of the pregnancies in these families.     

General solution of cable theory with both ends sealed

General solution of the cable theory with both ends sealed when injecting an arbitrary current at an arbitrary point of the cable is presented, which is a time-dependent transient solution. The solution is an infinite series, each term of which is the product of a cosine term including a position variable only and an exponential term including a time variable only. The general solution contains almost all solutions reported hitherto as particular cases and the mutual relations among the various solutions of quite different forms are clarified by this general solution. Moreover the shorter the cable becomes, the more rapidly this solution converges, therefore it is useful for an analysis of the short cable in the case where the relative deviation error may grow large. The truncation error can also be estimated as the solution is an infinite series of simple functions.     

Rights, indirect harms and the non-identity problem

The non‐identity problem is the problem of grounding moral wrongdoing in cases in which an action affects who will exist in the future. Consider a woman who intentionally conceives while on medication that is harmful for a fetus. If the resulting child is disabled as a result of the medication, what makes the woman's action morally wrong? I argue that an explanation in terms of harmful rights violations fails, and I focus on Peter Markie's recent rights‐based defense. Markie's analysis rests on the notion of an indirect harm, and I show that the calculation of an indirect harm relies on an improper baseline for the determination of whether or not an action adversely affects a patient's interests. I also defend an impersonal duty‐based analysis of the wrongdoing in non‐identity cases against an objection by Markie. I close by arguing that the rights‐based analysis is insensitive to context and that context is morally relevant in the determination of the moral valence of actions in cases of non‐identity. This failure provides a pro tanto reason to favor an impersonal duty‐based analysis of the wrongdoing in non‐identity cases.     

Echocardiography.

Imaging echocardiography is an important extension of the clinical examination and will answer most questions in an emergency-for example, whether an enlarged cardiac shadow on the chest radiograph represents ventricular dilatation or an effusion. Doppler ultrasonography is essential for hospitals with an interest in cardiology because it provides direct haemodynamic data that are complementary to imaging. It requires more skill than imaging and may also be time consuming. Colour flow Doppler mapping is speedy and simple to use and aids the interpretation of continuous wave Doppler. It is therefore a natural companion to conventional Doppler, but there would have to be a high clinical load to justify its purchase.     

Mode of action of tetrahydrolipstatin: a derivative of the naturally occurring lipase inhibitor lipstatin

Tetrahydrolipstatin is a specific lipase inhibitor derived from lipstatin, a lipid produced by Streptomyces toxytricini. In addition to pancreatic lipase, it is shown in the present study that tetrahydrolipstatin also inhibits human gastric lipase, carboxyl ester lipase (cholesterol esterase) of pancreatic origin and the closely related bile-salt-stimulated lipase of human milk. It does not inhibit the exocellular lipase from Rhizopus arrhizus or a lipase recently isolated from Staphylococcus aureus. In the presence of a water-insoluble substrate, such as tributyrin, the inhibition has the characteristics of an irreversible inactivation of the uncompetitive type, thus indicating that an enzyme.substrate.inhibitor complex is formed, which cannot undergo further reaction to yield the normal product. This reaction probably takes place at the aqueous/oil interface of the substrate. In aqueous solution, in the absence of substrate, the inhibition of carboxyl ester lipase by tetrahydrolipstatin has the characteristics of being reversible, and finally becomes of a temporary nature analogues to the trypsin-trypsin inhibitor system. It is suggested that an enzyme-inhibitor complex of an acyl-enzyme type is formed that is slowly hydrolysed, with water as the final acceptor, leaving an intact enzyme and an inactive form of the inhibitor. The enzyme thus consumes the inhibitor, which undergoes a chemical conversion, as indicated by a change in mobility in an appropriate thin-layer chromatographic system, indicating an increase in hydrophilicity. Evidence is presented that the reaction product is an acid and that the functional group of tetrahydrolipstatin is the beta-lactone reacting with the active site of the enzyme.     

The process of dissolving apolipoprotein A-I in an aqueous buffer

Human plasma apolipoprotein A-I (apoA-I) has been studied in an aqueous solution by the techniques of high performance liquid chromatography (HPLC), circular dichroic spectroscopy, and sedimentation equilibrium ultracentrifugation. The results indicate that an oligomer is formed as an intermediate step of dissolving lysophilized apoA-I. The process of further dissolution of this oligomer is an irreversible, temperature-dependent dissociation. The half-life of this intermediate oligomer is 3 min at 37 degrees C and 80 h at 30 degrees C. The completely dissolved apoA-I in an aqueous buffer self-associates with conformational alteration. The self-association equilibrium is too rapid to be demonstrated by HPLC.     

Fixed-bin analysis for statistical evaluation of continuous distributions of allelic data from VNTR loci, for use in forensic comparisons.

The detection of DNA polymorphisms by RFLP analysis is having a major impact on identity testing in forensic science. At present, this approach is the best effort a forensic scientist can make to exclude an individual who has been falsely associated with an evidentiary sample found at a crime scene. When an analysis fails to exclude a suspect as a potential contributor of an evidentiary sample, a means should be provided to assess suitable weight to the putative match. Most important, the statistical analysis should not place undue weight on a genetic profile derived from an unknown sample that is attributed to an accused individual. The method must allow for limitations in conventional agarose-submarine-gel electrophoresis and Southern blotting procedure, limited sample population data, possible subpopulation differences, and potential sampling error. A conservative statistical method was developed based on arbitrarily defined fixed bins. This approach permits classification of continuous allelic data, provides for a simple and portable data-base system, and is unlikely to underestimate the frequency of occurrence of a set of alleles. This will help ensure that undue weight is not placed on a sample attributed to an accused individual.     

Nonlinear theory of coupled waves exemplified by beam-plasma instability

The nonlinear stage of instability of an annular electron beam spatially separated from an annular plasma is investigated. The equations describing coupled waves for an arbitrary ratio between the beam and plasma densities are derived. It is shown that instability saturates at distances on the order of several inverse spatial growth rates. The saturation is caused by relativistic nonlinearity, generation of the second harmonic, and low-frequency modulation of the electromagnetic field. At larger distances, resonant generation of low-frequency beam oscillations becomes a dominant factor. In the case of a low-density beam, an expression for the maximum power of the generated plasma wave is obtained in an explicit form.     

Reconstructing an ultrametric galled phylogenetic network from a distance matrix

Given a distance matrix M that specifies the pairwise evolutionary distances between n species, the phylogenetic tree reconstruction problem asks for an edge-weighted phylogenetic tree that satisfies M, if one exists. We study some extensions of this problem to rooted phylogenetic networks. Our main result is an O(n(2) log n)-time algorithm for determining whether there is an ultrametric galled network that satisfies M, and if so, constructing one. In fact, if such an ultrametric galled network exists, our algorithm is guaranteed to construct one containing the minimum possible number of nodes with more than one parent (hybrid nodes). We also prove that finding a largest possible submatrix M' of M such that there exists an ultrametric galled network that satisfies M' is NP-hard. Furthermore, we show that given an incomplete distance matrix (i.e. where some matrix entries are missing), it is also NP-hard to determine whether there exists an ultrametric galled network which satisfies it.     

2-Acetylthiamin pyrophosphate: an enzyme-bound intermediate in thiamin pyrophosphate-dependent reactions

Several enzymes catalyze reactions that may involve acetylthiamin pyrophosphate (acetyl-TPP) as an intermediate. These enzymes are phosphoketolase, pyruvate oxidase and several pyruvate oxidoreductases. Acetyl-TPP can be synthesized and used as a carrier to analyze quenched reaction mixtures for the presence of [14C]acetyl-TPP. Synthetic acetyl-TPP exhibits unusual chemical properties and a unique pH-rate profile that serves as a powerful means of characterizing [14C]acetyl-TPP that has been isolated from quenched enzymatic reaction mixtures. Using this and other methods, extensive evidence has been obtained for the involvement of acetyl-TPP in certain reactions catalyzed by the pyruvate dehydrogenase complex (PDH complex) of Escherichia coli. Acetyl-TPP is chemically competent as an intermediate in the decarboxylation and dehydrogenation of pyruvate by the PDH complex; and it is transiently formed during the course of this reaction. It may be an enzyme-bound intermediate or it may be in equilibrium with such an intermediate. Acetyl-TPP is very likely to be an intermediate of the phosphoketolase reaction. However, no direct evidence linking it to the phosphoketolase reaction mechanism is yet available. It is unclear whether acetyl-TPP is an intermediate in the pyruvate oxidoreductase reactions. In one example, that of the ketoacid oxidoreductase of Halobacterium halobium, analysis by electron paramagnetic resonance spectroscopy indicates the involvement of a hydroxyethyl-TPP-radical as an intermediate. It is unknown whether the subsequent reaction of this radical with coenzyme A an an oxidized FeS cluster to produce acetyl coenzyme A and the reduced cluster involves the intermediate formation of acetyl-TPP.     

Fates-shifted is an F-box protein that targets Bicoid for degradation and regulates developmental fate determination in Drosophila embryos

Bicoid (Bcd) is a morphogenetic protein that instructs patterning along the anterior-posterior (A-P) axis in Drosophila melanogaster embryos. Despite extensive studies, what controls the formation of a normal concentration gradient of Bcd remains an unresolved and controversial question. Here, we show that Bcd protein degradation is mediated by the ubiquitin-proteasome pathway. We have identified an F-box protein, encoded by fates-shifted (fsd), that has an important role in Bcd protein degradation by targeting it for ubiquitylation. Embryos from females lacking fsd have an altered Bcd gradient profile, resulting in a shift of the fatemap along the A-P axis. Our study is an experimental demonstration that, contrary to an alternative hypothesis, Bcd protein degradation is required for normal gradient formation and developmental fate determination.     

Electrostatic potentials in membrane systems

A membrane with an arbitrary distribution of fixed charges inside and on its surfaces is considered. A procedure for calculating the local electrostatic potential at an arbitrary point of the system is described and its validity discussed. This procedure is based on the linearization of the 3-dimensional Poisson-Boltzmann equation around an exact 1-dimensional solution.     

The effect of error fields on the dynamics of a tearing mode in a tokamak

The features of the tearing mode dynamics in a tokamak that manifest themselves in an irregular mode rotation are demonstrated by using an algorithm for data processing that is based on the concept of the instantaneous frequency of an analytic signal. A model is developed in which the tearing mode is treated as an object to be controlled by means of an external quasistatic magnetic field with an appropriate spatial structure. It is shown that the model dynamics of the mode agrees well with the dynamics of tearing modes observed in experiments in which they are influenced by the magnetic field of the halo current.     

Protein phosphorylation in pancreatic islets: evidence for separate Ca2+ and cAMP-enhanced phosphorylation of two 57,000 Mr proteins

There is a phosphopeptide that has an Mr of 53,000 to 60,000 in insulin-secreting tissues and there is general agreement that this peptide can be phosphorylated in a calcium-dependent manner. The present report shows that there are at least two phosphoproteins with Mr's near 57,000 in rat pancreatic islet cytosol. One peptide has an Mr of 57,000, a pl of 7.5 - 8 and is phosphorylated in a Ca2+-enhanced manner, and the other has an Mr of 54,000, a pl of 5 - 5.5 and is phosphorylated in a cAMP-enhanced manner, as judged by two-dimensional polyacrylamide gel electrophoresis. Sepharose 4B chromatography indicated that the former polypeptide resides in a native protein complex that has an Mr of about 500,000 and the latter in a complex that has an Mr of about 180,000. Tritiated azido cyclic AMP binds to an islet polypeptide that has an Mr of 54,000. The results suggest that Ca2+ and cAMP could regulate stimulus-secretion coupling in pancreatic islets via protein phosphorylation.     

Evolutionary stability: States and strategies

Different aspects and modifications of the definition of an evolutionarily stable (ES) strategy that have been considered in the literature can be incorporated in a unifying concept which regards the population context. This concept of evolutionary stability will generally characterize population states in both pure- and mixed-strategist models. In particular, it includes ES strategies, represented as a phenotype unique in an ES population. For an important class of mixed-strategist models, no strict ESS can exist. This will be the case whenever the success of an individual strategy is considered to follow as an average from the successes of its behavioural components. Instead, ESS results may be obtained from what will be called a “degenerate” form of the model, which is simply an ESS model on the level of elementary actions. Then, however, the correct interpretation of an ESS is not an individual phenotype but rather a population mixture of elementary actions. If an ES state exists in a mixed-strategist model it may be determined by an equilibrium condition; if there is an ES strategy, a different approach—mainly maximum considerations—is needed for finding it. An equilibrium condition does not hold for the components of an ES strategy straightforwardly; but it can be derived in terms of an auxiliary ESS model that considers first-order effects of the components. Several examples illustrate the significance of these results. Particularly, two models on “Games between Relatives” are reconsidered in order to display both their formal interrelation and the different meaning of their results in the context of mixed-strategist models.