[Salter-Harris type IV epipyseal fracture of the lateral malleolus. A rare injury in childhood]

This is a case presentation of a 9-year-old boy who sustained a rare Salter-Harris type IV distal fibular fracture including an avulsion fracture of the anterior inferior tibiofibular ligament at the fibular attachment. Treatment consisted of open reduction and internal fixation by Kirschner wire and cerclage. Possible posttraumatic growth disturbances and the major implications are highlighted.

Sarcomas predominate in mice deficient for PrPc and p53

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Background: For cellular prion protein (PrPc) putative roles in many cellular processes including signalling, survival, adhesion, proliferation and differentation have been proposed. The hallmarks of cancer include some of these traits and in human tumors both increased and decreased levels of PrPc have been observed. However PrPc deficient mice show no increased rate of tumor formation. To characterize the possible role of PrPc in tumorigenesis we generated PrPc-/-/p53-/- mice. Methods: Organ and tumor samples were surgically removed post mortem and processed for histological analysis. Time to death was defined as the latency between birth and spontaneous death or a terminal disease state as indicated by tumor burden and other symptoms of severe disease. Results: As reported previously lymphomas are the most frequent tumors in p53-/- mice [5 out of 7 (71 %)]. In contrast, sarcomas predominate in PrPc-/-/p53-/- mice [9 out of 21 (43 %)]. This was accompanied by a decrease in the incidence of lymphomas in PrPc-/-/p53-/- mice [7 out of 21 (33 %)]. Conclusions: These results indicate for PrPc, in the context of p53 deficiency, a role in sarcoma tumorigenesis and the PrPc-/-/p53-/- mice might provide a clinical relevant model for the study of sarcomas.

No significant financial relationships to disclose.

Nociceptin/orphanin FQ peptide receptors: pharmacology and clinical implications

The advance of functional genomics revealed the superfamily of G-protein coupled receptors (GPCRs). Hundreds of GPCRs have been cloned but many of them are orphan GPCRs with unidentified ligands. The first identified orphan GPCR is the opioid receptor like orphan receptor, ORL1. It was cloned in 1994 during the identification of opioid receptor subtypes and was de-orphanized in 1995 by the discovery of its endogenous ligand, nociceptin or orphanin FQ (N/OFQ). This receptor was renamed as N/OFQ peptide (NOP) receptor. Several selective ligands acting at NOP receptors or other anti-N/OFQ agents have been reported. These include N/OFQ-derived peptides acting as agonists (cyclo[Cys(10),Cys(14)]N/OFQ, [Arg(14), Lys(15)]N/OFQ, [pX]Phe(4)N/OFQ(1-13)-NH(2), UFP-102, [(pF)Phe(4),Aib(7), Aib(11),Arg(14),Lys(15)]N/OFQ-NH(2)) or antagonists (Phe(1)psi(CH(2)-NH)Gly(2)]N/OFQ(1-13)-NH(2), [Nphe(1)]N/OFQ(1-13)-NH(2), UFP-101, [Nphe(1), (pF)Phe(4),Aib(7),Aib(11),Arg(14),Lys(15)]N/OFQ-NH(2)), hexapeptides, other peptide derivatives (peptide III-BTD, ZP-120, OS-461, OS-462, OS-500), non-peptide agonists (NNC 63-0532, Ro 64-6198, (+)-5a compound, W-212393, 3-(4-piperidinyl)indoles, 3-(4-piperidinyl) pyrrolo[2,3-b]pyridines) and antagonists (TRK-820, J-113397, JTC-801, octahydrobenzimidazol-2-ones, 2-(1,2,4-oxadiazol-5-yl)-1 H-indole, N-benzyl-D-prolines, SB-612111), biostable RNA Spiegelmers specific against N/OFQ, and a functional antagonist, nocistatin. Buprenorphine and naloxone benzoylhydrazone are two opioid receptor ligands showing high affinity for NOP receptors. NOP receptor agonists might be beneficial in the treatment of pain, anxiety, stress-induced anorexia, cough, neurogenic bladder, edema, drug dependence, and, less promising, in cerebral ischemia and epilepsy, while antagonists might be of help in the management of pain, depression, dementia and Parkinsonism. N/OFQ is also involved in cardiovascular, gastrointestinal and immune regulation. Altered plasma levels of N/OFQ have been reported in patients with various pain states, depression and liver diseases. This review summarizes the pharmacological characteristics of, and studies with, the available NOP receptor ligands and their possible clinical implications.

3-Azido-aspartic acid derivatives - orthogonally protected precursors for the stereoselective incorporation of 2,3-diaminosuccinic acid into peptide structures

The stereoselective synthesis of orthogonally protected 3-azido aspartic acid derivatives is described. The convenience of their application as 2,3-diaminosuccinic acid in peptide chemistry was demonstrated by the incorporation of the nonproteinogenic diamino diacid as a cystine-substitute into the core structure of somatostatin.

Reproducability and transferability of topological properties; experimental charge density of the hexapeptide cyclo-(D,L-Pro)2-(L-Ala)4 monohydrate

The charge density of a hexapeptide was determined from high-resolution CCD area-detector experiments at 100 K. Two datasets, one from a rotating anode and a second one from synchrotron radiation, were measured and the results are compared. The data are interpreted in terms of the 'rigid pseudoatom' model. The topology of the experimental density is analyzed and compared with the topology of the constituting amino acids, and shows good agreement. All critical points of the electron density at the covalent and hydrogen bonds, as well as those of the Laplacian, were located. With respect to the transferability of electronic and bond topological properties the six peptide bonds were compared with values given in the literature.

Cyclo19,31[D-Cys19]-uPA19-31 is a potent competitive antagonist of the interaction of urokinase-type plasminogen activator with its receptor (CD87)

Urokinase-type plasminogen activator (uPA) represents a central molecule in pericellular proteolysis and is implicated in a variety of physiological and pathophysiological processes such as tissue remodelling, wound healing, tumor invasion, and metastasis. uPA binds with high affinity to a specific cell surface receptor, uPAR (CD87), via a well defined sequence within the N-terminal region of uPA (uPA19-31). This interaction directs the proteolytic activity of uPA to the cell surface which represents an important step in tumor cell proliferation, invasion, and metastasis. Due to its fundamental role in these processes, the uPA/uPAR-system has emerged as a novel target for tumor therapy. Previously, we have identified a synthetic, cyclic, uPA-derived peptide, cyclo19,31uPA19-31, as a lead structure for the development of low molecular weight uPA-analogues, capable of blocking uPA/uPAR-interaction [Burgle et al., Biol. Chem. 378 (1997), 231-237]. We now searched for peptide variants of cyclo19,31uPA19-31 with elevated affinities for uPAR binding. Among other tasks, we performed a systematic D-amino acid scan of uPA19-31, in which each of the 13 L-amino acids was individually substituted by the corresponding D-amino acid. This led to the identification of cyclo19,31[D-Cys19]-uPA19-31 as a potent inhibitor of uPA/uPAR-interaction, displaying only a 20 to 40-fold lower binding capacity as compared to the naturally occurring uPAR-ligands uPA and its amino-terminal fragment. Cyclo19,31[D-Cys19]-uPA19-31 not only blocks binding of uPA to uPAR but is also capable of efficiently displacing uPAR-bound uPA from the cell surface and to inhibit uPA-mediated, tumor cell-associated plasminogen activation and fibrin degradation. Thus, cyclo19,31[D-Cys19]-uPA19-31 represents a promising therapeutic agent to significantly affect the tumor-associated uPA/uPAR-system.

A new strategy for the synthesis of cyclopeptides containing diaminoglutaric acid

A new synthesis of orthogonally protected diaminoglutaric acid containing peptides using the Ugi four component condensation is presented. To demonstrate that this method is useful to replace cystine by diaminoglutaric acid in biologically interesting peptides, we built up two cyclic somatostatin analogues deriving from Sandostatin and from TT-232. A photolytically cleavable amine derivative of the nitroveratryl type is used for the Ugi four component condensation. Because of a racemic build up of the new stereocentre of the diaminoglutaric acid, and racemization of the isonitrile component, four diastereomeric peptides resulted that were separated by HPLC. The stereochemistry of the cyclopeptides could be easily and unambiguously assigned by chiral gas chromatography and a reference sample of enantiomerically pure (2S,4S)-diaminoglutaric acid.

Databases of human hemoglobin variants and other resources at the globin gene server

Building on the pioneering efforts of Professor Huisman, several different databases of hemoglobin variants have been developed, each with progressively increased capacity for sophisticated queries and prompt updating. These resources are reviewed in the context of a larger plan for providing related resources on hemoglobins, benign and pathological variation in these proteins and the genes that encode them, and the regulation of the globin genes.

Comparative analysis of the gene-dense ACHE/TFR2 region on human chromosome 7q22 with the orthologous region on mouse chromosome 5

Chromosome 7q22 has been the focus of many cytogenetic and molecular studies aimed at delineating regions commonly deleted in myeloid leukemias and myelodysplastic syndromes. We have compared a gene-dense, GC-rich sub-region of 7q22 with the orthologous region on mouse chromosome 5. A physical map of 640 kb of genomic DNA from mouse chromosome 5 was derived from a series of overlapping bacterial artificial chromosomes. A 296 kb segment from the physical map, spanning ACHE: to Tfr2, was compared with 267 kb of human sequence. We identified a conserved linkage of 12 genes including an open reading frame flanked by ACHE: and Asr2, a novel cation-chloride cotransporter interacting protein Cip1, Ephb4, Zan and Perq1. While some of these genes have been previously described, in each case we present new data derived from our comparative sequence analysis. Adjacent unfinished sequence data from the mouse contains an orthologous block of 10 additional genes including three novel cDNA sequences that we subsequently mapped to human 7q22. Methods for displaying comparative genomic information, including unfinished sequence data, are becoming increasingly important. We supplement our printed comparative analysis with a new, Web-based program called Laj (local alignments with java). Laj provides interactive access to archived pairwise sequence alignments via the WWW. It displays synchronized views of a dot-plot, a percent identity plot, a nucleotide-level local alignment and a variety of relevant annotations. Our mouse-human comparison can be viewed at http://web.uvic.ca/~bioweb/laj.html. Laj is available at http://bio.cse.psu.edu/, along with online documentation and additional examples of annotated genomic regions.

5-HT(6) receptor antagonists: lead optimisation and biological evaluation of N-aryl and N-heteroaryl 4-amino-benzene sulfonamides

RO-04-6790 (6a) has been identified in a random screen for 5-HT(6) receptor antagonists. In a medicinal chemistry optimisation program a series of analogs comprising N-heteroaryl- and N-arylbenzenesulfonamides have been synthesised and investigated for their binding affinity. Compounds with a logD profile indicative of brain penetration have been subjected to in vivo testing for reversal of a scopolamine-induced retention deficit in a passive avoidance paradigm.

Identification of upregulated genes in scrapie-infected brain tissue

The pathogenesis of scrapie, and of neurodegenerative diseases in general, is still insufficiently understood and is therefore being intensely researched. There is abundant evidence that the activation of glial cells precedes neurodegeneration and may thus play an important role in disease development and progression. The identification of genes with altered expression patterns in the diseased brain may provide insight on the molecular level into the process which ultimately leads to neuronal loss. Differentially expressed genes in scrapie-infected brain tissue were enriched by the suppression subtractive hybridization technique, molecularly cloned, and further characterized. Northern blotting and nucleotide sequencing confirmed the identities of 19 upregulated genes, 11 of which were unknown to be affected by scrapie. A considerable number of these 19 genes, namely those encoding interferon-inducible protein 10 (IP-10), 2',5'-oligo(A) synthetase, Mx protein, IIGP protein, major histocompatibility complex classes I and II, complement, and beta(2)-microglobulin, were inducible by interferons (IFNs), suggesting that an IFN response is a possible mechanism of gene activation in scrapie. Among the newly found genes, that coding for 2',5'-oligo(A) synthetase is of special interest because it could contribute to the apoptotic loss of neuronal cells via RNase L activation. In addition, upregulation of the chemokine IP-10 and B-lymphocyte chemoattractant mRNAs was seen at relatively early stages of the disease and was sustained throughout disease development.

Web-based visualization tools for bacterial genome alignments

With the increase in the flow of sequence data, both in contigs and whole genomes, visual aids for comparison and analysis studies are becoming imperative. We describe three web-based tools for visualizing alignments of bacterial genomes. The first, called Enteric, produces a graphical, hypertext view of pairwise alignments between a reference genome and sequences from each of several related organisms, covering 20 kb around a user-specified position. Insertions, deletions and rearrangements relative to the reference genome are color-coded, which reveals many intriguing differences among genomes. The second, Menteric, computes and displays nucleotide-level multiple alignments of the same sequences, together with annotations of ORFs and regulatory sites, in a 1 kb region surrounding a given address. The third, a Java-based viewer called Maj, combines some features of the previous tools, and adds a zoom-in mechanism. We compare the Escherichia coli K-12 genome with the partially sequenced genomes of Klebsiella pneumoniae, Yersinia pestis, Vibrio cholerae, and the Salmonella enterica serovars Typhimurium, Typhi and Paratyphi A. Examination of the pairwise and multiple alignments in a region allows one to draw inferences about regulatory patterns and functional assignments. For example, these tools revealed that rffH, a gene involved in enterobacterial common antigen (ECA) biosynthesis, is partly deleted in one of the genomes. We used PCR to show that this deletion occurs sporadically in some strains of some serovars of S.enterica subspecies I but not in any strains tested from six other subspecies. The resulting cell surface diversity may be associated with selection by the host immune response.

PipMaker--a web server for aligning two genomic DNA sequences

PipMaker (http://bio.cse.psu.edu) is a World-Wide Web site for comparing two long DNA sequences to identify conserved segments and for producing informative, high-resolution displays of the resulting alignments. One display is a percent identity plot (pip), which shows both the position in one sequence and the degree of similarity for each aligning segment between the two sequences in a compact and easily understandable form. Positions along the horizontal axis can be labeled with features such as exons of genes and repetitive elements, and colors can be used to clarify and enhance the display. The web site also provides a plot of the locations of those segments in both species (similar to a dot plot). PipMaker is appropriate for comparing genomic sequences from any two related species, although the types of information that can be inferred (e.g., protein-coding regions and cis-regulatory elements) depend on the level of conservation and the time and divergence rate since the separation of the species. Gene regulatory elements are often detectable as similar, noncoding sequences in species that diverged as much as 100-300 million years ago, such as humans and mice, Caenorhabditis elegans and C. briggsae, or Escherichia coli and Salmonella spp. PipMaker supports analysis of unfinished or "working draft" sequences by permitting one of the two sequences to be in unoriented and unordered contigs.

Comparison of five methods for finding conserved sequences in multiple alignments of gene regulatory regions

Conserved segments in DNA or protein sequences are strong candidates for functional elements and thus appropriate methods for computing them need to be developed and compared. We describe five methods and computer programs for finding highly conserved blocks within previously computed multiple alignments, primarily for DNA sequences. Two of the methods are already in common use; these are based on good column agreement and high information content. Three additional methods find blocks with minimal evolutionary change, blocks that differ in at most k positions per row from a known center sequence and blocks that differ in at most k positions per row from a center sequence that is unknown a priori. The center sequence in the latter two methods is a way to model potential binding sites for known or unknown proteins in DNA sequences. The efficacy of each method was evaluated by analysis of three extensively analyzed regulatory regions in mammalian beta-globin gene clusters and the control region of bacterial arabinose operons. Although all five methods have quite different theoretical underpinnings, they produce rather similar results on these data sets when their parameters are adjusted to best approximate the experimental data. The optimal parameters for the method based on information content varied little for different regulatory regions of the beta-globin gene cluster and hence may be extrapolated to many other regulatory regions. The programs based on maximum allowed mismatches per row have simple parameters whose values can be chosen a priori and thus they may be more useful than the other methods when calibration against known functional sites is not available.

A database of experimental results on globin gene expression

Information on gene expression and regulation is expanding rapidly, and the complexity of the experimental design and data makes unique demands on databases to store the results. We describe a prototype database containing experimental results on the expression of mammalian beta-like globin genes, along with several query methods for accessing the information. The database has tables for DNA transfer experiments, protein-DNA binding results, and positions of DNase hypersensitive sites, which make extensive use of nested data structures. Comparison of data from various mammals is accomplished by providing a common coordinate system via a simultaneous alignment of matching DNA sequences. Interactive access to the database is available at a site called the Globin Gene Server on the World Wide Web (http://globin.cse. psu.edu). This software should be useful for any genetic system in which DNA sequence data are available.

The 5-hydroxytryptamine6 receptor-selective radioligand [3H]Ro 63-0563 labels 5-hydroxytryptamine receptor binding sites in rat and porcine striatum

Ro 63-0563 [4-amino-N-(2,6 bis-methylamino-pyridin-4-yl)-benzene sulfonamide] is a high affinity 5-hydroxytryptamine6 (HT6) receptor antagonist with more than 100-fold selectivity for the 5-HT6 receptor compared with 69 other receptors and binding sites. The present study describes the properties of [3H]Ro 63-0563, the first selective 5-HT6 receptor radioligand. Specific binding of [3H]Ro 63-0563 (nonspecific binding defined in the presence of 10 microM methiothepin) to recombinant rat and human 5-HT6 receptors was saturable, rapid, and reversible with equilibrium dissociation constants (Kd) of 6.8 nM and 4.96 nM, respectively. The pharmacological profile of the rat 5-HT6 receptor labeled with [3H]Ro 63-0563 (methiothepin > D-lysergic acid diethylamide > clozapine approximately Ro 63-0563 > lisuride > ergotamine approximately Ro 04-6790 > 5-HT > amitriptyline approximately metergoline approximately mianserin approximately ritanserin > methysergide > mesulergine) was similar to that obtained by using either [3H]D-lysergic acide diethylamide or [3H]5-HT as radioligand. In equilibrium binding studies with rat striatal membranes, [3H]Ro 63-0563 labeled a single binding site with Kd and Bmax values of 11. 7 nM and 175 fmol/mg protein, respectively. In porcine striatal membranes, [3H]Ro 63-0563 also labeled a single binding site with Kd and Bmax values of 8.0 nM and 130 fmol/mg protein, respectively. The affinities of 14 5-HT6 receptor ligands at this binding site were similar to those found for the recombinant rat and human 5-HT6 receptor, which suggested the presence of 5-HT6 receptors in porcine striatum.

Characterization of Ro 04-6790 and Ro 63-0563: potent and selective antagonists at human and rat 5-HT6 receptors

1. This study describes the in vitro characterization of two potent and selective 5-HT6 receptor antagonists at the rat and human recombinant 5-HT6 receptor. 2. In binding assays with [3H]-LSD, 4-amino-N-(2,6 bis-methylamino-pyrimidin-4-yl)-benzene sulphonamide (Ro 04-6790) and 4-amino-N-(2,6 bis-methylamino-pyridin-4-yl)-benzene sulphonamide (Ro 63-0563) had mean pKi values +/-s.e.mean at the rat 5-HT6 receptor of 7.35+/-0.04 and 7.83+/-0.01, respectively and pKi values at the human 5-HT6 receptor of 7.26+/-0.06 and 7.91+/-0.02, respectively. 3 .Both compounds were found to be over 100 fold selective for the 5-HT6 receptor compared to 23 (Ro 04-6790) and 69 (Ro 63-0563) other receptor binding sites. 4. In functional studies, neither compound had any significant effect on basal levels of cyclicAMP accumulation in Hela cells stably expressing the human 5-HT6 receptor, suggesting that the compounds are neither agonists nor inverse agonists at the 5-HT6 receptor. However, both Ro 04-6790 and Ro 63-0563 behaved as competitive antagonists with mean +/-s.e.mean pA2 values of 6.75+/-0.07 and 7.10+/-0.09, respectively. 5. In rats habituated to observation cages, Ro 04-6790 produced a behavioural syndrome similar to that seen following treatment with antisense oligonucleotides designed to reduce the expression of 5-HT6 receptors. This behavioural syndrome consisted of stretching, yawning and chewing. 6. Ro 04-6790 and Ro 63-0563 represent valuable pharmacological tools for the identification of 5-HT6 receptors in natural tissues and the study of their physiological function.

Epitope-mapped monoclonal antibodies as tools for functional and morphological analyses of the human urokinase receptor in tumor tissue

uPAR (CD87), the receptor for the urokinase-type plasminogen activator (uPA) facilitates tumor cell invasion and metastasis by focusing uPA proteolytic activity to the cell surface. As uPAR exists in various molecular forms, it is desirable to use well defined antibodies for analyses of uPAR antigen expression in human malignant tumors by immunological methods. Therefore, twelve monoclonal antibodies (MAbs) directed against uPAR were generated by using nonglycosylated, recombinant human uPAR (spanning amino acids 1 to 284), expressed in Escherichia coli, as the immunogen. The reaction pattern of these MAbs with the immunogen and a series of carboxyl-terminally truncated versions of uPAR demonstrated that at least six different epitopes of uPAR are recognized. All MAbs reacted under reducing conditions in immunoblot analyses with E. coli-expressed uPA and also with highly glycosylated, functionally intact, recombinant human uPAR expressed in Chinese hamster ovary (CHO) cells. Seven of the MAbs recognized CHO uPAR under nonreducing conditions as well. By flow cytofluorometric analyses, three of these MAbs were shown to bind to native human uPAR present on the cell surface of monocytoid U937 cells with MAb IIIF10 being the best. Saturation of uPAR with uPA on U937 cells completely blocked interaction of MAb IIIF10 with uPAR (mapped epitope, amino acids 52 to 60 of domain I of uPAR). In turn, preincubation of U937 cells with MAb IIIF10 efficiently reduced binding of uPA to uPAR, indicating that the epitope detected by MAb IIIF10 is located within or closely to the uPA-binding site of uPAR, and thus, this site may be a target to influence uPA/uPAR-mediated proteolysis in tumors. Binding of MAbs IID7 or IIIB11 (mapped epitope, amino acids 125 to 132 of domain II of uPAR) to uPAR is not affected when uPAR is occupied by uPA. As these MAbs reacted strongly with cellular uPAR antigen in formalin-fixed paraffin-embedded tumor sections, the domain-II-specific antibodies IID7 and IIIB11 may be useful for immunohistochemical studies of uPAR expression in tissue remodeling processes in tumor invasion. In conclusion, we have devised well defined and epitope-mapped MAbs to uPAR that are highly specific tools for detection and targeting of uPAR in tumor tissue.

Inhibition of the interaction of urokinase-type plasminogen activator (uPA) with its receptor (uPAR) by synthetic peptides

Focusing of the serine protease urokinase-type plasminogen activator (uPA) to the cell surface via interaction with its specific receptor (uPAR, CD87) is an important step for tumor cell invasion and metastasis. The ability of a synthetic peptide derived from the uPAR-binding region of uPA (comprising amino acids 16-32 of uPA; uPA(16-32)) to inhibit binding of fluorescently labeled uPA to uPAR on human promyeloid U937 cells was assessed by quantitative flow cytofluorometric analysis (FACS) and compared to the inhibitory capacities of other synthetic peptides known to interfere with uPA/uPAR-interaction. An about 3000-fold molar excess of uPA(16-32) resulted in 50% inhibition of pro-uPA binding to cell surface-associated uPAR. Using a solid-phase uPA-ligand binding assay employing recombinant soluble uPAR coated to microtiter plates, the minimal binding region of wild-type uPA was determined. The linear peptide uPA(19-31) and its more stable disulfide-bridged cyclic form (cyclo(19,31)uPA(19-31)) displayed uPAR-binding activity whereas other peptides such as uPA(18-30), uPA(20-32) or uPA(20-30) did not react with uPAR. Cyclic peptide derivatives of cyclo(19,31)uPA(19-31) in which certain amino acids were deleted and/or replaced by other amino acids as well as uPAR-derived wild-type peptides did also not inhibit uPA/uPAR-interaction. Therefore, the present investigations identified cyclo(19,31)uPA(19-31) as a potential lead structure for the development of uPA-peptide analogues to block uPA/uPAR-interaction.

Design, synthesis and biological activity of protaxols

Taxol is a product isolated from the Pacific yew tree (Taxus brevifolia) and is a potent microtubule-stabilizing agent which has recently been approved for treatment of otherwise intractable ovarian cancer. Despite taxol's therapeutic promise, its aqueous insolubility (< 0.004 mg ml-1) hampers its clinical application. Here we report the design, synthesis and biological activity of a series of taxol-releasing compounds (protaxols) with improved pharmacological properties. These prodrugs were designed to increase their aqueous solubility and allow for taxol release under basic or physiological conditions. We demonstrate the stability of these prodrugs at pH < or = 7 and their ability to release taxol in a basic medium. Taxol-like microtubule-stabilizing activity appears after the release of taxol. In vitro these prodrugs have cytotoxic properties against tumour cell lines comparable to those of taxol; moreover, human plasma catalyses the release of active taxol. These protaxols have greater potential as anticancer agents than the parent compounds taxol and taxotere (Fig. 1a).