Separation and Characterization of Surfactin Isoforms Produced by Bacillus subtilis OKB 105

Natural surfactin is a mixture of cyclic lipopeptides built from variants of a heptapeptide and a beta-hydroxy fatty acid with chain lengths of 13-15 carbon atoms. The lipopeptide biosurfactant was produced by Bacillus subtilis OKB 105 and part of the material subjected to esterification of its Glu and Asp residues. High-resolution preparative reversed phase HPLC on EnCaPharm 100 of surfactin and its monomethyl and dimethyl esters yielded 44 fractions which were characterized by NMR and MS methods. Among the separated isoforms are the known surfactin variants with l-Leu, l-Val, or l-Ile in position 7 of the peptide ring and three hitherto unknown variants showing replacements of the leucine residues in position 2 and/or 7 by l-Val and l-Ile. Our work makes available lipoheptapeptide compounds with modified structures and different hydrophobicities which promise to have potential for biotechnological and pharmaceutical applications. Copyright 1998 Academic Press.

Characterization of the binding site of the tripeptide intermediate D-Phenylalanyl L-prolyl-L-valine in gramicidin S biosynthesis

The tripeptide intermediate D-Phe-Pro-Val in the biosynthesis of gramicidin S was labeled by incorporation of either L-[14C]phenylalanine or L-[14C]valine in an in vitro biosynthetic assay. The gramicidin S synthetase 2-tripeptide complex was first digested with CNBr and subsequently by Staphylococcus aureus V8 protease. The active site peptide carrying the radioactively labeled tripeptide was isolated in pure form by reversed phase high performance liquid chromatography technology and analyzed by liquid phase sequencing, mass spectrometry, and amino acid analysis. It was demonstrated that D-Phe-Pro-Val is attached to the 4'-phosphopantetheine cofactor at the thiolation center for valine of gramicidin S synthetase 2. In this way the attachment site of a peptide intermediate in nonribosomal peptide biosynthesis was identified for the first time. Our results are in full agreement with the multiple carrier model of nonribosomal peptide biosynthesis (Stein, T., Vater, J., Kruft, V., Otto, A., Wittmann-Liebold, B., Franke, P., Panico, M., McDowell, R., and Morris, H. R. (1996) J. Biol. Chem. 271, 15426-15435), which predicts that the growing peptide chain in the elongation process should always be bound to the thiotemplate site specific for its C-terminal amino acid component.

[New method of MR-guided mammary biopsy]

PURPOSE

With a recently installed new open MR tomograph (Signa SP, General Electric MS) it is possible for the first time to examine patients with obscure lesions of the mamma by MR imaging in a sitting position, similar to mammography.

METHOD

The newly developed positioning device with integrated surface coil permits in combination with the vertical gap in the new magnet and imaging of the mamma with a "real time" sequence a biopsy procedure within a short time and in a manner that is acceptable for the patient. By means of an integrated interactive scan plane guiding system ("flash point tracking system") and special MR-compatible needles and wires tissue samples can be taken, or marking by a wire can be carried out within a short time.

RESULTS

Phantom experiments and first in vivo experience (10 patients) show that by means of the new mamma fixation and biopsy device a MRI of one breast in a sitting position for detecting an enhancing lesion and a MR-guided biopsy of this lesion is possible. The whole procedure takes about 25-35 minutes, comparable to the conventional stereotactic method.

CONCLUSION

Direct patient access and the interactive guided biopsy allow in future both new diagnostic information (histological results after biopsy or after wire-guided open biopsy of a lesion only visible in MR) and the development of minimal invasive therapeutic procedures, e.g. MR-guided and -controlled interstitial thermotherapy.

Labeling of Torpedo californica nicotinic acetylcholine receptor subunits by cobratoxin derivatives with photoactivatable groups of different chemical nature at Lys23

Different photoactivatable derivatives of toxin 3 (CTX) Naja naja siamensis were obtained after CTX reaction with N-hydroxysuccinimide esters of p-azidobenzoic, p-azidotetraflourobenzoic, p-benzoylbenzoic and p-[3-(trifluoromethyl)-3H-diazirin-3-yl]benzoic acids. The ion-exchange HPLC profiles for the reaction products were very similar in four cases, with one predominant peak corresponding to the derivative containing the label at Lys23. After [125I]iodination, CTX photoactivatable derivatives were cross-linked to the nicotinic acetylcholine receptor from Torpedo californica under optimized conditions. The highest cross-linking yield (up to 16% of the bound toxin) was observed for azidobenzoyl-Lys23-CTX. Different receptor subunits were found to be labelled depending on the nature of the photoactivatable group: the azido derivatives labelled the gamma and delta subunits, benzoylbenzoyl derivative labelled the alpha and delta subunits, while p-[3-(trifluoromethyl)-3H-diazirin-3-yl]benzoyl derivative reacted with alpha, gamma and delta subunits. The cross-linking experiments in the presence of varying concentrations of (+)-tubocurarine demonstrated that the Lys23-attached diazirinyl group contacts the delta and alpha subunits in one ligand-binding site, whereas at the other site, for another CTX molecule, the contacts of the Lys23-diazirinyl are with gamma and alpha subunits. This means that the central loop in the two CTX molecules binds at the alpha/gamma and alpha/delta interfaces. Calculation of the sterically possible displacement of diazirinyl nitrogen, basing on the known X-ray structure of CTX, showed that this value does not exceed 13 A. The results obtained favor the disposition of the ligand-binding sites at the subunit interfaces, with the distance between alpha and delta, or alpha and gamma subunits at these sites being not more than 13 A.

Reverse-phase chromatography isolation and MALDI mass spectrometry of the acetylcholine receptor subunits

A procedure for purifying the Torpedo californica nicotinic acetylcholine receptor subunits is proposed which involves preparative SDS-PAGE followed by reverse-phase HPLC on a C4 column in an acetonitrile-isopropanol system. By this method, the alpha-subunit can be completely separated from the 43-kDa protein which migrates very close to it on SDS-PAGE, and the delta-subunit can be isolated free from the beta-subunit of Na+, K(+)-ATPase comigrating with it on SDS-PAGE. The purity of all acetylcholine receptor subunits thus obtained was verified by Edman degradation and MALDI mass-spectrometric analysis which could be performed quite easily on the HPLC-purified samples. In general, we observed a good correlation between the experimentally determined molecular masses and those calculated from the amino acid sequences and when known, posttranslational modifications (glycosylation and phosphorylation) of individual receptor subunits. Transfer of the isolated receptor subunits into 1% octyl-beta-D-glucopyranoside generates samples suitable for functional studies and enzymatic proteolysis or deglycosylation.

The accessible surface of the nicotinic acetylcholine receptor. Identification by chemical modification and cross-linking with 14C-dimethyl suberimidate

To obtain structural information on the nicotinic acetylcholine receptor from Torpedo electric tissue we modified and cross-linked lysine residues with the agonistic bifunctional reagent [14C]dimethyl suberimidate. This reagent labels exposed lysine residues, especially those located near the ligand-binding site, and cross-links lysine residues located not more than 11 A, the length of the cross-linker, apart. Using this method, we identified a cross-link located between betaLys177 and betaLys191 showing that the 13 amino acids in between form a loop with these two residues located at the surface. Cross-linking also occurred between the vicinal lysine residues alphaLys76 and alphaLys77, indicating that these neighbouring lysine residues are not involved in a beta-sheet structure. A total of 21 out of 97 lysine residues present in the receptor were modified by [14C]dimethyl suberimidate. Thus these residues are located on the accessible extramembrane surface. The two lysine residues alphaLys76 and alphaLys179 were predominantly labelled. Because of the agonistic property of [14C]dimethyl suberimidate [Watty, A., Methfessel, C. & Hucho, F. (1997) Proc. Natl Acad. Sci. USA 94, 8202-8209] this might be due to their close proximity to the ligand binding site.

Purification and characterization of N-acetylglucosamine kinase from rat liver--comparison with UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase

N-Acetylglucosamine, a major sugar in complex carbohydrates, enters the pathways of aminosugar metabolism by the action of N-acetylglucosamine kinase (EC 2.7.1.59). In this study we report the purification to homogeneity of GlcNAc kinase from rat liver cytosol using salmine sulfate precipitation, chromatography on phenyl-Sepharose, ATP-agarose and MonoQ, and finally gel filtration on Superdex 200. It was characterized as a dimer of 39-kDa subunits. About 25% of the amino acid sequence of GlcNAc kinase was established by peptide mapping. Part of the ATP-binding site of GlcNAc kinase was identified by sequence comparison with related hexokinases, including the bifunctional enzyme UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (EC 5.1.3.14/2.7.1.60), the key enzyme of N-acetylneuraminic acid biosynthesis in rat liver. The Cys residues in the active sites of GlcNAc kinase and ManNAc kinase were characterized by chemical modification with N-ethylmaleimide, iodoacetamide and 5,5'-dithiobis(2-nitrobenzoic acid). The finding that the substrates GlcNAc and ManNAc protected their respective enzymes from inhibition by the above sulfhydryl reagents indicates that Cys residues are located in or near the active sites of both enzymes. Use of the specific dithiol-modifying chemical reagents, sodium meta-periodate, sodium meta-arsenite/2,3-dimercaptopropanol and diazenedicarboxylic acid bis-N,N'-dimethylamide revealed that the active sites of GlcNAc kinase and ManNAc kinase possess at least one pair of vicinal thiols. Chemical treatment of UDP-GlcNAc 2-epimerase provided no evidence for the presence of cysteine in the active site of this enzyme. From the incorporation of N-[3H]ethylmaleimide into GlcNAc kinase in the absence and presence of ligands we estimated that the active site of GlcNAc kinase contains two Cys residues.

Systematic mutation screening and association study of the A1 and A2a adenosine receptor genes in panic disorder suggest a contribution of the A2a gene to the development of disease

Several lines of evidence suggest a contribution of adenosinergic neurotransmission to the development of panic disorder. We therefore hypothesized that variation in the A1 and A2a adenosine receptor (AR) genes modifies genetic susceptibility to panic disorder. To test this hypothesis, we screened 38 patients with panic disorder for mutations in the coding sequence of the A1AR and A2aAR genes. An association study between the identified DNA sequence variants and panic disorder was performed in an extended sample of 89 patients and matched controls. One silent mutation (716T/G) in the A1AR gene and two silent mutations (432C/T and 1083C/T) in the A2aAR gene were detected. The association sample shows a significant association between the 1083T allele (P=0.01) and 1083T/T genotype (P=0.024) of the A2AR gene and panic disorder. Our findings thus lend further support to the hypothesis that the A2aAR gene, or a locus in linkage disequilibrium with it, confers susceptibility to panic disorder. Replication studies in independent samples with nuclear families applying the transmission disequilibrium test (TDT) are warranted.

Substance P derivatives with photoactivatable labels in the N-terminal part of the molecule

Photoactivatable substance P (SP) derivatives containing the p-benzoylbenzoic moiety at the N-terminal alpha-amino group of Arg 1 or at the epsilon-amino group of Lys 3 were prepared. Both derivatives also had a p-hydroxyphenylpropionyl group for radioiodination. To obtain the analogue with the photolabel at Arg 1, SP was first reacted with N-hydroxysuccinimide p-hydroxyphenylpropionate, the Lys 3-modified derivative was isolated by reversed-phase high-performance liquid chromatography (HPLC), reacted with N-hydroxysuccinimide p-benzoylbenzoate and purified by HPLC. To place the photolabel at Lys 3, the order of the reactions was reversed. The structure of the derivatives obtained was confirmed by mass spectrometry. The interaction of the derivatives obtained and of their 125I-labeled forms with the NK-1 neurokinin receptor from the rat brain, as well as with the nicotinic acetylcholine receptor from Torpedo electrocytes was analyzed. The results obtained supported by the data from the literature indicate that benzoylbenzoic acid derivatives should not be considered as universal photolabels, which ensure in all cases a high level of photo-cross-linking.

Intra- and interhemispheric electroencephalogram coherence in siblings discordant for schizophrenia and healthy volunteers

Former studies had pointed to an increased electroencephalogram (EEG) coherence in schizophrenics, but it remained unsolved whether this deviation represents the premorbid state or is only a consequence of the current or previous schizophrenic episodes. To clarify this question, we tested the hypothesis that subjects at elevated risk also reveal higher coherences compared to healthy controls. For that, intra- and interhemispheric EEG coherences were investigated in untreated schizophrenics, their healthy siblings, and healthy controls. Differences were only found regarding the intrahemispheric coherences. Both in schizophrenics and, even though to a lesser degree, in their siblings significantly higher coherence estimates were found compared to the control group. The results are in accordance with the assumption that schizophrenia is predominantly a neurodevelopmental disease. Increased coherence might be assumed to be a vulnerability marker for schizophrenia reflecting maldevelopment of the brain before onset of the disorder.

The modular organization of multifunctional peptide synthetases

Gramicidin S synthetase 2 from B. brevis was affinity labeled at its valine thiolation center with the thiol reagent N-[3H]ethylmaleimide. From a tryptic digest of the enzyme-inhibitor complex a radioactive fragment was isolated in pure form by two reversed-phase HPLC steps. It was identified by liquid-phase N-terminal sequencing in combination with electrospray mass spectrometry (ESI-MS) as a hexadecapeptide containing the thiolation motif LGG(H/D)S(L/I). By ESI-MS it was demonstrated that a 4'-phosphopantetheine cofactor was attached to this fragment at its reactive serine. These results are consistent with the "Multiple Carrier Model" of nonribosomal peptide biosynthesis. Site-specific mutagenesis has been performed in thiolation, elongation, and epimerization motifs of some of the modules of surfactin synthetase from B. subtilis to clarify the function of prominent conserved amino acid residues in the intermediate steps of peptide biosynthesis. The modular structure of multifunctional peptide synthetases is discussed.

The glycosylated matrix protein of Borna disease virus is a tetrameric membrane-bound viral component essential for infection

Borna disease virus (BDV) is representative of the family of Bornaviridae in the order Mononegavirales (negative-stranded, non-segmented, enveloped RNA viruses). It is the causal agent for Borna disease, characterized as an encephalomyelitis (typical form) in a wide variety of domestic animals (from rodents to birds). Recent information shows the involvement of BDV in the pathogenesis of some human psychiatric disorders. The 8.9-kb viral antigenome codes for five major ORF. The third ORF codes for a 16-kDa protein (matrix protein) that is posttranslationally modified, yielding an N-linked glycoprotein. Our data show that the glycosylated matrix protein exists as a stable tetrameric structure detectable either by electrospray ionization or matrix-assisted laser-desorption ionization mass spectrometry. Under native conditions, the tetramer, with a relative molecular mass of 68 kDa, was isolated from a sediment-free brain suspension of a BDV-infected horse. The 68-kDa entity is stable in the presence of ionic and nonionic detergents but dissociates into subunits when heated. We found that the tetrameric matrix protein inhibits in vitro BDV infection in a dose-dependent manner. In contrast to inhibition of BDV infection with hydrophobic carbohydrate derivatives and protein-bound glycoconjugates, the glycosylated matrix protein is a very potent inhibitor of BDV infection, indicating that this protein represents an essential virus-specific membrane component for viral attachment.

Neuronal nicotinic acetylcholine receptor alpha 4 subunit (CHRNA4) and panic disorder: an association study

Anxiety disorders have been reported to be associated with low-voltage EEG (LVEEG). Some cases with LVEEG (approximately 1/3) have been linked to chromosome 20q13.2q13.3. In the same chromosomal region, the gene for the neuronal nicotinic acetylcholine receptor alpha 4 subunit (CHRNA4) has been located. We therefore tested the hypothesis that polymorphisms in the CHRNA4 gene show an allelic association with panic disorder. We examined the allele frequencies of three different CHRNA4 polymorphisms in patients with panic disorder and in healthy controls. No significant differences in the allele frequencies of these three polymorphisms were noted. This study does not support an association between panic disorder and the CHRNA4 gene.

Functional promoter polymorphism of the human serotonin transporter: lack of association with panic disorder

To probe the hypothesis of a role for a functionally relevant 44 bp insertion/deletion of the serotonin transporter promoter in the aetiopathogenesis of panic disorder, we determined the allele frequency of the variant in two samples (combined n = 158) of panic disorder patients (DSMIII-R) and compared it with its allele frequency in two ethnically matched control samples (combined n = 169). The fact that no difference could be observed (x 2 analysis) argues against a major role for this serotonin transporter promoter polymorphism in the aetiopathogenesis of panic disorder.

Mapping of exposed surfaces of the nicotinic acetylcholine receptor by identification of iodinated tyrosine residues

Here we report on the use of iodination of the membrane-bound nicotinic acetylcholine receptor (nAChR) from Torpedo californica electric tissue in order to define surface-exposed portions of the receptor molecule. Membrane-bound nAChR was 125I-iodinated using the oxidation agent Iodo-Gen. The iodinated subunits were separated by preparative gel electrophoresis, desalted, and cleaved with trypsin. The resulting peptides were separated by reverse-phase HPLC and the radioactive peptides were identified by mass spectrometry and protein sequencing. For the delta-subunit, we identified five iodinated peptides containing the tyrosine residues deltaTyr17, deltaTyr74, deltaTyr365, deltaTyr372, and deltaTyr428. The surface exposition of these amino acids is in agreement with the four-transmembrane-segment model (4TM model) of the nAChR, but the assignment to the intra- or extracellular surface is doubtful. According to this model, the N-terminal portion of the receptor subunits including the iodinated residues deltaTyr17 and deltaTyr74 is extracellular and deltaTyr372 as a site of tyrosine phosphorylation is located on the cytoplasmic side. But since this latter residue is among the first to be iodinated using an immobilized iodination agent, its true position with respect to the membrane bilayer is not clear.

Purification, structural analysis, and function of natural ATAC, a cytokine secreted by CD8(+) T cells

Recently, we identified a novel putative human cytokine expressed by activated CD8(+) T cells, which was designated ATAC (activation-induced, T cell-derived, and chemokine-related; the same molecule has been identified independently as lymphotactin and single cysteine motif-1). In this report, we provide evidence that ATAC is a secreted 93-amino acid protein that is generated from its precursor by proteolytic cleavage between Gly21 and Val22. An estimated 60% of ATAC (Val22-Gly114) is secreted as an unmodified protein with a molecular mass of 10,271.72 Da (apparent molecular mass of 12 kDa in SDS-polyacrylamide gel electrophoresis) and in which Cys32 and Cys69 are linked by a disulfide bridge. Unmodified ATAC is a cationic protein with a pI of 11.35 and is capable of binding to heparin. Some 40% of ATAC is O-glycosylated within 25 min of synthesis, giving rise to the appearance of a homogeneous 15-kDa (minor fraction) and a heterogeneous, terminally sialylated 17-19-kDa (major fraction) protein species in SDS-polyacrylamide gel electrophoresis. The secretion of all ATAC protein variants is completed within 30-40 min of synthesis. In terms of function, various ATAC protein forms were consistently ineffective in chemotaxis assays. In contrast, both purified natural ATAC and a chemically synthesized aglycosyl analog induced locomotion (chemokinesis) in purified CD4(+) and CD8(+) T cell populations at 400 ng/ml.

Structure analysis of acetylated and non-acetylated O-linked MUC1-glycopeptides by post-source decay matrix-assisted laser desorption/ionization mass spectrometry

We have investigated the potential of structural elucidation of O-linked glycopeptides by post-source decay matrix-assisted laser desorption ionization mass spectrometry (PSD-MALDI-MS). In order to establish detailed fragmentation patterns and to dissect fragment ions with and without carbohydrate content, the same O-linked MUC1-derived glycopeptides with acetylated and non-acetylated sugars were analysed and compared. Furthermore, we were interested to examine possible differences in the fragmentation between glycopeptides with acetylated and non-acetylated sugars. The obtained PSD-MALDI-MS spectra showed a rather complete set of fragmentation data which allows to localize the glycan on the peptide, in parallel with sequencing a short glycan and the backbone peptide. Fragmentations of the sugars were dominated by inter-ring cleavages at the glycosidic bond. Intra-ring cleavage did also occur from the non-reducing end, but to a much lower extent. The fragmentation of the peptide backbone was not changed either by acetylated or non-acetylated sugars. Glycosylated peptide fragments occurred as fully glycosylated fragment ions, partially deglycosylated ions and completely deglycosylated ions, and was not influenced by the acetylation of sugars. However, differences occurred in the quality and quantity of fragment ions from the non-reducing end of the glycan part when comparing acetylated with non-acetylated glycopeptides.

Fragile-X carrier females: evidence for a distinct psychopathological phenotype?

The present study examined 35 mothers (29 premutation carriers) of children with fragile-X syndrome in measures of intelligence and psychiatric disorders by comparing them with two control groups: a) 30 mothers of children in the general population and b) 17 mothers of non-fra-X retarded children with autism. Premutation carriers had a higher frequency of affective disorders than mothers from the general population. Preliminary data indicate that normally intelligent premutation carriers of the fra-X genetic abnormality have a similar frequency of affective disorders (DSM-III-R criteria [APA, 1987]) than mothers of autistic children. Neither carriers of the premutation nor carriers of the full mutation in the fra-X group obtained a diagnosis of the schizophrenia-spectrum (schizophrenia, schizophreniform disorder, and schizoaffective disorder). Carriers of the fra-X full mutation had considerably lower IQ than carriers of the fra-X premutation. There was a negative correlation between length of CGG repeats and IQ which failed to reach significance in both groups of fra-X carriers. Psychiatric morbidity was not restricted to carriers of the fra-X full mutation only but was also present in normal intelligent premutation carriers. Furthermore the age of onset of psychiatric morbidity in both groups of mothers of fra-X children as well as the group of mothers with autistic children was much earlier than the age when mental retardation had been diagnosed in their children. Increased psychosocial burden of raising a developmentally retarded child and/or feelings of guilt of being a fra-X carrier can therefore not fully explain our findings (three-fold higher frequencies of affective disorders compared to mothers from the general population).

The multiple carrier model of nonribosomal peptide biosynthesis at modular multienzymatic templates

Gramicidin S synthetase 1 and 2 were affinity-labeled at their thiolation centers either by thioesterification with the amino acid substrate or by specific alkylation with the thiol reagent N-ethylmaleimide in combination with a substrate protection technique. The labeled proteins were digested either chemically by cyanogen bromide or by proteases. An efficient multistep high pressure liquid chromatography methodology was developed and used to isolate the active site peptide fragments of all five thiolation centers of gramicidin S synthetase in pure form. The structures of these fragments are investigated by N-terminal sequencing, mass spectrometry, and amino acid analysis. Each of the active site peptide fragments contains the consensus motif LGG(H/D)S(L/I), which is specific for thioester formation in nonribosomal peptide biosynthesis. It was demonstrated that a 4'-phosphopantetheine cofactor is attached to the central serine of the thiolation motif in each amino acid-activating module of the gramicidin S synthetase multienzyme system forming the thioester binding sites for the amino acid substrates and catalyzing the elongation process. Our data are strong support for a "multiple carrier model" of nonribosomal peptide biosynthesis at multifunctional templates, which is discussed in detail.

[Biotransformation of the lipoxygenase inhibitor 2-hydroxy-5-methyl-laurophenone-oxime (FLM 5011)]

2-Hydroxy-5-methyl-laurophenone-oxime (FLM 5011, 1) is an inhibitor of the lipoxygenase with antiinflammatory and antiallergic actions. The studies on the biotransformation using in vivo investigations and in vitro test systems resulted in finding of at least eight metabolites. Four of these compounds have been detected and identified in urine and faeces after p.o. administration in male Wistar rats. By means of cultures of hepatocytes, lymphocytes and myeloma cells additional metabolites were found and the main pathways of metabolism could be suggested. Furthermore it was possible to confirm the sequence of the metabolic reactions. First of all, 1 is hydroxylated in the omega-position of the lauryl side chain by the cytochrome P-450 system. The further oxidation to the carboxylated compound is followed by the stepwise degradation of the side chain by beta-oxidation similarly to the pathways of fatty acid metabolism. Simultaneously the oxime group is converted to the keto group. The metabolites and 1 partly occur as sulfate or glucuronide conjugates. Additionally all compounds produced by beta-oxidation are conjugated with other partners, probably amino acids. By omega-oxidation, compounds with higher inhibitory potency on the lipoxygenase than the parent compound are formed. These results suggest that the activity of 1 is partly caused by the initial metabolites.

Force magnitude applied by orthodontists. An inter- and intra-individual study

The aim of this investigation was to study the magnitude and variation of forces routinely applied by different orthodontists for buccal tipping of premolars and canines in the maxilla, and also to compare these forces with the individually considered ideal force. Nineteen clinically experienced orthodontists were asked to bend and activate sectional arch wires on a plastic model with bands on the first molars. Round 0.016 Australian wires were used on one side and square 0.016 x 0.016 Blue Elgiloy wires on the other. The tests were repeated a second time 3-4 weeks later. The applied mean force magnitude was 48.4 cN (g) for premolars and 40.0 cN for canines, with a considerable intra-individual variation (range 25-75 cN, and 21-62 cN) using the round Australian wire. In general, the activation of the square wire resulted in a higher force, mean difference 29 per cent (11.4 cN) for canines and 23 per cent (11.1 cN) for premolars when compared with the round wire. On each side, the shorter wire for premolars was activated with a higher force when compared with the longer canine wire, mean 16 per cent (8.0 cN) for the square wire and 21 per cent (8. cN) for the round wire. Sex, age and clinical experience had no major influence on the applied force magnitude. On average, the orthodontists considered an ideal force for tipping of canines and premolars to be mean 62.5 cN (range 30-100 cN) and mean 56.1 cN (range 30-100 cN) respectively. They also reported that a strain gauge was not often used in everyday clinical practice. This study showed substantial differences between applied forces and considered ideal forces. It is suggested that regular checks of the force magnitude should be performed in situations where a certain force is considered important.

Citric acid extracts a specific set of proteins from isolated cell nuclei

The treatment of isolated cell nuclei with citric acid was described as a method for separating inner and outer nuclear membrane. Using cell nuclei from bovine cerebral cortex, we can show that citric acid does not cause a separation of the two nuclear membranes, but extracts a specific set of proteins from the nuclei. The extraction of proteins is not just an effect of damaging the nuclear membrane or destructing the cytoskeleton, but rather a specific effect of citric acid treatment. One of the extracted proteins, chosen as a marker for the putative outer nuclear membrane fraction, has an apparent molecular weight of 145 kDa and is located in the nucleoplasm as shown by immunofluorescence microscopy. By sequencing tryptic peptides it was identified as RNA helicase A, an abundant nuclear protein assumed to participate in the processing of mRNA.