Anabaena flos-aquae NRC 525-17 produces a very potent neurotoxin, anatoxin-a(s). During isolation of the neurotoxin, we found that the strain contains four other toxic compounds which show strong hepatotoxicity. The four toxins, toxins 1, 1', 2, and 3, were successfully purified. Toxin 2, one of major toxins, was identified as 3-desmethylmicrocystin LR (1) by comparison of spectral data of the known compound. Since the three other toxins contain an unknown amino acid, GC/MS was applied and it revealed the presence of homotyrosine in toxins 1 (2) and 1' (3). Only a partial structure was obtained for toxin 3 due to the small amount present in the cells.

Using a monoclonal antibody that recognizes a nuclear matrix protein, we selected a cDNA clone from a gt11 human placenta cDNA library. This cDNA encoded a 939-amino acid protein designated nuclear matrix protein NXP-2. Northern blot analysis indicated that NXP-2 was expressed in various tissues at different levels. Forcibly expressed green fluorescent protein-tagged NXP-2 as well as endogenous NXP-2 was localized in the nucleus and distributed to the nuclear matrix. NXP-2 was released from the nuclear matrix when RNase A was included in the buffer for nuclear matrix preparation. Mapping of functional domains was carried out using green fluorescent protein-tagged truncated mutants of NXP-2. The region of amino acids 326 -353 was responsible for nuclear matrix binding and contained a cluster of hydrophobic amino acids that was similar to the nuclear matrix targeting signal of acute myeloleukemia protein. The central region (amino acids 500 -591) was demonstrated to be required for RNA binding by Northwestern analysis, although NXP-2 lacked a known RNA binding motif. The region of amino acid residues 682-876 was predicted to have a coiled-coil structure. The RNA-binding, nuclear matrix-binding, and coiled-coil domains are structurally separated, suggesting that NXP-2 plays important roles in diverse nuclear functions, including RNA metabolism and maintenance of nuclear architecture.The nuclear matrix is involved in the structural organization of chromatin and the integrity of the nucleus (1-3). In addition, DNA replication, RNA processing, and gene transcription have been suggested to be associated with the nuclear matrix. There are many reports of chromatin binding to the nuclear matrix during replication (4 -10), as well as the enrichment of transcribed genes in this nuclear subcompartment (11-15). The DNA-nuclear matrix interaction seems to be mediated by chromatin-associated proteins such as topoisomerase II (3), matrixassociated region-binding proteins such as hnRNPU (16), and SATB1 (17). These proteins are capable of binding to A/T-rich DNA regions (3,16,17). It was reported that the hSWI/SNF protein complex involved in the remodeling of chromatin during gene activation could be associated with the nuclear matrix attachment region (18). The nuclear matrix may act as an active structure on which gene expression takes place (for review, see Ref. 9). On the basis of experimental observations, it has been suggested that actively transcribing nucleotideprotein complex is associated with the nuclear matrix (7, 19 -22) and that posttranscriptional processing of nascent transcripts takes place in association with the nuclear matrix (23, 24). Recently, protein mass spectrometry of the interchromatin granule, a subfraction of the nuclear matrix, identified many RNA-binding proteins involved in RNA processing (25).These results suggest that the nuclear matrix constitutes various dynamic nuclear substructures involved in diverse nuclear functions. To clarify the functional roles of the nuclear matrix, more protein comp...

This paper is concerned with chatter in tandem cold rolling mills, which has been recognised to have close relation with friction conditions in roll bites. However, the relation between rolling conditions and the stability of vibration has not been clearly understood. Therefore, an attempt is made to understand how the rolling conditions can be related with vibration phenomena, through numerical simulations.Firstly, a theoretical model is constituted to simulate the vibrational behaviour of a five-stand continuous rolling mill, and the stability of the mill vibration is evaluated, introducing a disturbance to the static rolling conditions. The results of the calculation show that the vibration is greatly influenced by rolling speed and friction coefficient. With increase in rolling speed, the mill vibration tends to be self-excited. Also, the results show that optimal range of friction coefficient exists in which the vibration is damped and the mill is stable against the disturbance.Secondly, a simple self-exited vibration model is proposed and the stability index is proposed for further understanding of the phenomena. An analytical approach is made to predict the stability of the rolling process. With this model, it is shown that the rolling force and the delay of the response to the change in gap have a major effect on self-exited vibration. Also, the calculated optimal range of friction coefficient in the continuous rolling simulation can be explained by using the analytical model.

The outer membranepermeability-increasing action of deacylpolymyxins was comparedto the well-known potent action of polymyxin B nonapeptide (PMBN). Deacylpolymyxin B (DAPB), prepared by treating polymyxin B with polymyxin acylase, was found to be a slightly more effective permeabilizer than PMBN. As low a DAPBconcentration as 1 /*g/ml sensitized Escherichia coli to the probe antibiotics (rifampin, fusidic acid, erythromycin, clindamycin, novobiocin) by factors 30~100 and Salmonella typhimurium by factors 10~100. A higher concentration (3 /Jg/ml) ofDAPB elicited further sensitization. Also deacylcolistin (DAC)was found to be an effective permeabilizer.Chihara and co-workers1>2) have shown that the terminal TV-fatty acyl amino acid moiety can be removed from polymyxin (PM) using ficin or papain to yield a PM-derived nonapeptide (Fig. 1). ThisPMnonapeptide lacks the bactericidal activity of the parent compound. It was then found by Vaara and Vaara3~5) and confirmed by others6~9), that PMnonapeptides still have one important property left, viz., they drastically damage the outermost cell wall structure (the outer membrane: OM) ofGram-negative bacteria and increase its permeability to hydrophobic antibiotics. However, it is not very clear, how selectively papain and ficin act in the hydrolysis of PM. In the light of the results of Chihara et al. (Table 7 in

Polymyxin B octapeptide (PBOP) and polymyxin B heptapeptide (PBHP) were found to be effective permeabilizers of the outer membraneof Escherichia coli and Salmonella typhimurium. PBOP was as effective as polymyxin B nonapeptide (PMBN), the known very potent permeabilizer. As low a PBOPconcentration as 1 /zg/ml sensitized E. coli to rifampicin by a factor of 100. Three /xg ofPBOP per ml was sufficient to sensitize this target to all the other tested hydrophobic antibiotics (erythromycin, fusidic acid, clindamycin, and novobiocin) by a factor of 30. Only a slightly higher (3-fold) concentration of PBHPwas required for a similar sensitizing effect.The outer membrane(OM)of Gram-negative enteric bacteria and Pseudomonasaeruginosa is an effective permeability barrier towards noxious drugs including antibiotics1}. Agents such as divalent chelators and certain polycations are knownto damage and permeabilize the OMand to sensitize the cell to many of those drugs. Chelators remove the stabilizing divalent cations inherent in the OMwhereas polycations bind to the acidic lipopolysaccharide constituent of the OM1}. While the OM permeability-increasing action of chelators is severely blocked by physiologically relevant concentrations of cations2), that of the most potent polycations (such as polymyxin B nonapeptide, PMBN)is not2).Polymyxin nonapeptides (five positive charges, 5 +) are significantly less toxic in animal studies than polymyxins3~6), but able to sensitize, usually at as low concentrations as l~3 //g, the target bacteria to lipophilic antibiotics (such as erythromycin, clindamycin, rifampicin and fusidic acid) by a factor of 303 qq7~ii) AlsQ deaCyipOiymyXmsi2) (6+), the lysine polymer with approx 20 residues8'9) (20+) and the arginine-rich peptide protamine8)9) (17+) are effective sensitizers, while the permeabilizing activity of aminoglycosides (streptomycin; 3+, gentamicin; 5+) is weak or absent in biologically relevant conditions8'13) (numbers in parentheses indicate the net charge). Weakor very weak permeabilizers also include pentalysine13) (5+) and the human granulocyte defensins14) (5 +). Polyamines, including spermine (4+),are not permeabilizers8). Perhaps surprisingly, linear polymyxin-resembling synthetic peptides (linear arginylpolymyxin B decapeptide; 6 + , linear lysylpolymyxin B nonapeptide; 5 + ) also lack the activity1 5).In order to develop an effective and possibly therapeutically useful polycationic permeabilizer, it should be important to evaluate which factors (total number of positive charges, charge density, favorable conformation of the polycation) are critical for the OM-permeabilizing activity. Wewill show in this communication that the OMpermeability-increasing potency of the octapeptide derivative (5+) of