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K Leonhard

Publications and source records attributed to K Leonhard.

At least 19 recordsLinked to original sources
PubMed2006

Three-dimensional lattice Monte Carlo simulations of model proteins. IV. Proteins at an oil-water interface.

Lattice Monte Carlo simulations describe the adsorption of protein-like heteropolymer chains at an oil/water interface. The heteropolymers are designed sequences of 27 and 64 amino acid-type lattice sites taken from a 20-letter alphabet. We use our recently suggested energy scale to model oil and water. We investigate the effect of the oil parameters on adsorption properties of a single chain and on the aggregation of adsorbed chains while keeping the water parameters fixed to their optimum values found previously. By varying the oil parameters, we can cause a large range of adsorption behavior: from no adsorption to reversible adsorption to irreversible adsorption. We compare adsorption at a liquid/solid interface to that at a liquid/liquid interface. A liquid interface leads to stronger adsorption and denaturation than a solid interface with the same water and oil interaction parameters. We propose "optimal" oil parameters and use them to study multichain adsorption at a liquid interface.

Adsorption↗
PubMed2003

3D-Lattice Monte Carlo simulations of model proteins. Size effects on folding thermodynamics and kinetics.

Recently, we devised an energy scale to vary systematically amino-acid residue-solvent interactions for Monte Carlo simulations of lattice-model proteins in water. For 27-mer proteins, the folding behavior varies appreciably with the choice of interaction parameters. We now perform similar simulations with 64-mers to study the size dependence of the optimal energy parameter set for representing realistic behavior typical of many real proteins (i.e. fast folding and high cooperativity for single chains). We find that 64-mers are considerably more stable and more cooperative compared to 27-mers. The optimal interfacial-interaction-energy parameter set, however, is relatively size independent.

Amino Acid Sequence↗
PubMed2003

Treatment of landfill leachate--high tech or low tech? A case study.

At the sanitary landfill of the city of Penzberg (Germany), two diverse approaches to leachate treatment were studied as parts of a three-stage treatment concept. The performance of a simple aerobic pond was compared to that of an advanced multistage treatment unit, the latter comprising a membrane biological reactor and a two-stage activated carbon filter. For 274 days of the year (75%) the pond was able to provide sufficient treatment even under cold weather conditions. For temperatures lower than 5 degrees C, a higher biomass content and temporal storage of the raw leachate (e.g. increasing hydraulic retention time) could close the gap of insufficient treatment. In contrast, the advanced treatment system could only accomplish limited treatment capabilities due to insufficient maintenance, low loading conditions and deficient coordination between the individual treatment steps. As a result, degradation rates were low and operational problems frequent. Limits for Ntot were exceeded regularly (Ntot,e = 60-70 mg/L), throughput broke down and excessive nitrite production occurred (NO2-Ne = 10 mg/L) as a result of microbial activity inside the activated carbon filters. This case study clearly suggests aerobic ponds as an appropriate solution for the treatment of landfill leachate in areas where operational independence is essential.

Bacteria, Aerobic↗
PubMed2001

Mba1, a novel component of the mitochondrial protein export machinery of the yeast Saccharomyces cerevisiae.

The biogenesis of mitochondria requires the integration of many proteins into the inner membrane from the matrix side. The inner membrane protein Oxa1 plays an important role in this process. We identified Mba1 as a second mitochondrial component that is required for efficient protein insertion. Like Oxa1, Mba1 specifically interacts both with mitochondrial translation products and with conservatively sorted, nuclear-encoded proteins during their integration into the inner membrane. Oxa1 and Mba1 overlap in function and substrate specificity, but both can act independently of each other. We conclude that Mba1 is part of the mitochondrial protein export machinery and represents the first component of a novel Oxa1-independent insertion pathway into the mitochondrial inner membrane.

Cell Division↗
PubMed2001

Role of the ABC transporter Mdl1 in peptide export from mitochondria.

ATP-binding cassette (ABC) adenosine triphosphatases actively transport a wide variety of compounds across biological membranes. Here, the ABC protein Mdl1 was identified as an intracellular peptide transporter localized in the inner membrane of yeast mitochondria. Mdl1 was required for mitochondrial export of peptides with molecular masses of approximately 2100 to 600 daltons generated by proteolysis of inner-membrane proteins by the m-AAA protease in the mitochondrial matrix. Proteolysis by the i-AAA protease in the intermembrane space led to the release of similar-sized peptides independent of Mdl1. Thus, two pathways of peptide efflux from mitochondria exist that may allow communication between mitochondria and their cellular environment.

ATP-Binding Cassette Transporters↗
PubMed2001

AAA proteases of mitochondria: quality control of membrane proteins and regulatory functions during mitochondrial biogenesis.

An ubiquitous and conserved proteolytic system regulates the stability of mitochondrial inner membrane proteins. Two AAA proteases with catalytic sites at opposite membrane surfaces form a membrane-integrated quality control system and exert crucial functions during the biogenesis of mitochondria. Their activity is modulated by another membrane-protein complex that is composed of prohibitins. Peptides generated upon proteolysis in the matrix space are transported across the inner membrane by an ATP-binding cassette transporter. The function of these conserved components is discussed in the present review.

Chloroplasts↗
PubMed2000

Membrane protein degradation by AAA proteases in mitochondria: extraction of substrates from either membrane surface.

Two AAA proteases, each with its catalytic site at the opposite membrane surface, mediate the ATP-dependent degradation of mitochondrial inner membrane proteins. We demonstrate here that a model substrate polypeptide containing hydrophilic domains at both sides of the membrane can be completely degraded by either of the AAA proteases, if solvent-exposed domains are in an unfolded state. A short protein tail protruding from the membrane surface is sufficient to allow the proteolytic attack of an AAA protease that facilitates domain unfolding at the opposite side. Our results provide a rationale for the membrane arrangement of AAA proteases in mitochondria and demonstrate that degradation of membrane proteins by AAA proteases involves an active extraction of transmembrane segments and transport of solvent-exposed domains across the membrane.

Adenosine Triphosphatases↗
PubMed1999

Chaperone-like activity of the AAA domain of the yeast Yme1 AAA protease.

The AAA domain, a conserved Walker-type ATPase module, is a feature of members of the AAA family of proteins, which are involved in many cellular processes, including vesicular transport, organelle biogenesis, microtubule rearrangement and protein degradation. The function of the AAA domain, however, has not been explained. Membrane-anchored AAA proteases of prokaryotic and eukaryotic cells comprise a subfamily of AAA proteins that have metal-dependent peptidase activity and mediate the degradation of non-assembled membrane proteins. Inactivation of an orthologue of this protease family in humans causes neurodegeneration in hereditary spastic paraplegia. Here we investigate the AAA domain of the yeast protein Yme1, a subunit of the iota-AAA protease located in the inner membrane of mitochondria. We show that Yme1 senses the folding state of solvent-exposed domains and specifically degrades unfolded membrane proteins. Substrate recognition and binding are mediated by the amino-terminal region of the AAA domain. The purified AAA domain of Yme1 binds unfolded polypeptides and suppresses their aggregation. Our results indicate that the AAA domain of Ymel has a chaperone-like activity and suggest that the AAA domains of other AAA proteins may have a similar function.

ATP-Dependent Proteases↗
PubMed1996

AAA proteases with catalytic sites on opposite membrane surfaces comprise a proteolytic system for the ATP-dependent degradation of inner membrane proteins in mitochondria.

The mechanism of selective protein degradation of membrane proteins in mitochondria has been studied employing a model protein that is subject to rapid proteolysis within the inner membrane. Protein degradation was mediated by two different proteases: (i) the m-AAA protease, a protease complex consisting of multiple copies of the ATP-dependent metallopeptidases Yta1Op (Afg3p) and Yta12p (Rcalp); and (ii) by Ymelp (Ytallp) that also is embedded in the inner membrane. Ymelp, highly homologous to Yta1Op and Yta12p, forms a complex of approximately 850 kDa in the inner membrane and exerts ATP-dependent metallopeptidase activity. While the m-AAA protease exposes catalytic sites to the mitochondrial matrix, Ymelp is active in the intermembrane space. The Ymelp complex was therefore termed 'i-AAA protease'. Analysis of the proteolytic fragments indicated cleavage of the model polypeptide at the inner and outer membrane surface and within the membrane-spanning domain. Thus, two AAA proteases with their catalytic sites on opposite membrane surfaces constitute a novel proteolytic system for the degradation of membrane proteins in mitochondria.

ATP-Dependent Proteases↗
PubMed1990

Catamnesis of endogenous psychoses according to the differential diagnostic method of Karl Leonhard.

The validity of the current systems of classification of endogenous psychoses has not yet been unambiguously demonstrated using the criterion of prognosis. An alternative to these systems may be seen in the Leonhard classification of endogenous psychoses. In a catamnestic study, 93% of the initial diagnoses and prognoses made between 1969 and 1973 could be confirmed in 1986.

Bipolar Disorder↗
PubMed1990

[Differential diagnosis of endogenous psychoses in relation to a symptom catalog].

The paper introduces a catalog of symptoms to promote in the field of endogenous psychoses differentiated diagnosis, at the same time constituting a prognosis. Symptoms should be more minutely differentiated than is customary in psychiatric questionnaires. Manic-depressive disorders and purely phasal psychoses are distinguished solely in the clinical evaluation. Thus benign cycloid psychoses can be distinguished from malignant unsystematic schizophrenia.

Bipolar Disorder↗
PubMed1989

[Goethe, Kant, Locke, Villaume knew our technic of individual therapy].

John Locke (1632-1704) and Villaume (1746-1825) were already familiar with the method with which we, in our "individual therapy", treat neurotic patients. The question whether conditional reflexes and the elimination of their effects play an essential part in the procedure must be denied.

Behavior Therapy↗
PubMed1987

[Differential diagnosis and different etiologies of monopolar and bipolar phasic psychoses].

Monopolar and bipolar phasic psychoses can be differentiated not only on the course but also on the symptom pattern. This applies also to the euphoric forms which usually are still assigned to Manic-depressive illness. The differential diagnosis is presented. Aetiology is completely different in the monopolar and the bipolar phasic psychoses. Manic-depressive illness has a hereditary basic, whereas in the monopolar ("pure") forms loading is very low. Particularly few psychoses among the relatives have been found in the euphoric forms which demonstrates their independency for if they would belong to Manic-depressive illness they necessarily would show the heavy genetic loading of this bipolar illness. In the pure phasic psychoses external causes were detected when we focused on the sibships in which the probands had grown up. The euphoric patients had relatively many older siblings, the depressive ones relatively few older siblings. A similar difference was found in two cycloid psychoses. Transcultural observations as well as shifts in the incidence rate of the psychoses in our times confirmed our results. Prophylactic measures can be derived.

Bipolar Disorder↗
PubMed1986

[Has the cataphasic form of schizophrenia increased in modern times?].

According to our investigations the incidence of cataphasia, which is a subtype of schizophrenia, has become more common in the last years and on average, has started earlier in life. As the central disorder of this illness concerns thinking perhaps there exists a relation of our finding to the rapid modern development of techniques, insofar as the cognitive function is overstrained in childhood and adolescence, when the nervous system has not matured yet. Introverted individuals seem to be at a particular risk. However, it must not be disregarded that cataphasia is an inherited illness which cannot be caused by external influences, but can only be promoted in its manifestation.

Cognition Disorders↗