The longest, regular polypeptide 3(10) helix at atomic resolution.

A synthetic, terminally blocked homodecapeptide from the C alpha, alpha-dimethylated glycyl residue alpha-aminoisobutyric acid has been analyzed by single-crystal X-ray diffraction and the structure refined to R = 0.073. The compound crystallizes as a perfect 3(10) helix, stabilized by eight consecutive intramolecular N-H . . . O = C hydrogen bonds. This is the first observation at atomic resolution of a regular polypeptide 3(10) helix as long as three complete turns.

Molecular dynamics simulation in vacuo and in solution of [Aib5,6-D-Ala8] cyclolinopeptide A: a conformational and comparative study.

The conformation of a Cyclolinopeptide A analogue, c-(Pro-Pro-Phe-Phe-Aib-Aib-Ile-D-Ala-Val), has been investigated by means of molecular dynamics simulations, in various molecular environments. The molecular dynamics results are compared with that obtained for Cyclolinopeptide A and a detailed analysis of the different behaviour for the two compounds is reported. A complete analysis of hydrogen bonds is presented.

Structure and dynamics of elastin building blocks. Boc-LG-OEt, Boc-VGG-OH.

Short di- and tripeptides such as Boc-LG-OEt, Boc-VG-OEt and Boc-VGG-OH, corresponding to abundant repetitive sequences in elastin, have been extensively studied both in solid state, by X-ray diffraction, and in solution by circular dicroism and nuclear magnetic resonance. Furthermore, theoretical procedures such as simulated annealing and molecular dynamics were also performed on these peptides. In general, the results indicate that no one single structure (be folded or extended) could be representative for these sequences in the protein, but rather that a multiplicity of interconverting conformers, ranging from folded to extended structures, should be considered. In any case, these structures, e.g. beta-turns, polyglycine II and beta-conformations, are those previously suggested to participate to conformational equilibria of elastin.

Molecular structure of peptaibol antibiotics: solution conformation and crystal structure of the octapeptide corresponding to the 2-9 sequence of emerimicins III and IV.

The infrared absorption and 1H nuclear magnetic resonance analyses of chloroform solutions of the terminally-blocked segment corresponding to the 2-9 sequence of emerimicins III and IV, -(Aib)3-L-Val-Gly-L-Leu-(Aib)2-, are consistent with the presence of a 3(10)-helical structure of high thermal stability. The crystal structure of the octapeptide, obtained by X-ray diffraction indicates the formation of a right-handed 3(10)-helix, stabilized by six consecutive intramolecular N-H....O:C H-bonds, slightly distorted at the level of the L-Leu residue.

Critical main-chain length for conformational conversion from 3(10)-helix to alpha-helix in polypeptides.

To assess the minimal peptide length required for the stabilization of the alpha-helix relative to the 3(10)-helix in Aib-rich peptides, we have solved the X-ray diffraction structures of the terminally blocked sequential hexa- and octapeptides with the general formula-(Aib-L-Ala)n-(n = 3 and 4, respectively). The hexapeptide molecules are completely 3(10)-helical with four 1----4 intramolecular N-H . . . O = C H-bonds. On the other hand, the octapeptide molecules are essentially alpha-helical with four 1----5 H-bonds; however, the helix is elongated at the N-terminus, with two 1----4 H-bonds, giving these molecules a mixed alpha/3(10)-helical character. In both compounds the right-handed screw sense of the helix is dictated by the presence of the Ala residues of L-configuration. This study represents the first experimental proof for a 3(10)----alpha-helix conversion in the crystal state induced by peptide backbone lengthening only.

Long, chiral polypeptide 3(10)-helices at atomic resolution.

The crystal-state preferred conformation of the terminally blocked hepta- and octapeptides with the general formula -(Aib)n L-Leu-(Aib)2- (n = 4 and 5, respectively), determined by X-ray diffraction, was found to be a right-handed 3(10)-helix stabilized by five and six consecutive intramolecular NH...O = C H-bonds of the C(10)-III type, respectively. The octapeptide structure represents the first observation at atomic resolution of a regular, chiral 3(10)-helix larger than two complete turns. In both cases the right handed screw sense of the helix is dictated by the presence of the single, internal L-residue. This study confirms the propensity of short peptides rich in Aib, the prototype of the amino acid residues dialkylated at the alpha carbon, to adopt a 3(10)-helical structure and is expected to help our understanding of the conformational preferences of the membrane-active, channel-forming, ion-transporting peptaibol antibiotics.

Neoadjuvant chemotherapy or chemotherapy and endocrine therapy in locally advanced breast carcinoma. A prospective, randomized study.

Forty-nine patients with locally advanced breast carcinoma were prospectively randomized to be treated with either CMF or CMF plus T for four courses, both before and after mastectomy. The overall clinical objective remission rate for induction treatment was similar (71% with CMF and 64% with CMF + T). The time to progression or recurrence of the disease was also not significantly different between the two groups. Overall survival was shorter after CMF + T treatment (median value of 41.5 months) than after CMF treatment alone (median value of 79.7 months; p = 0.05). Even after progression or recurrence, survival was shorter for patients receiving CMF + T than those receiving CMF (median values of 7.5 and 17.3 months, respectively; p = 0.09). These results show that the addition of T to CMF in the treatment of locally advanced breast carcinoma, before and after mastectomy, offers no advantage for improving the overall response rate. Moreover, this addition may have an adverse impact on survival in this disease setting.

Mature results of a prospective randomized trial comparing a three-weekly with an accelerated weekly schedule of cisplatin in advanced ovarian carcinoma.

In a retrospective analysis of a series of clinical trials by Levin and Hryniuk in 1987, the average relative dose intensity of first-line chemotherapy for advanced ovarian cancer correlated significantly with clinical response and survival, and cisplatin was the only drug for which the outcome correlated with the individual drug relative dose intensity. There was a need to test whether and to what extent this evidence would be confirmed in a prospective evaluation. In this study 101 patients with advanced ovarian carcinoma were randomized to receive the same total dose of cisplatin but at the conventional 3-weekly schedule (CTWS) (100 mg/m2 every 3 weeks for six cycles) (51 patients) or at an experimental accelerated weekly schedule (AWS) (100 mg/m2 every week for two triplets of three cycles separated by a 5-week interval) (50 patients). To benefit from a multidrug regimen at the same extent, patients in both arms sequentially received four cycles of doxorubicin and cyclophosphamide. The median follow-up period of this study is 9.7 years. In 42 and 40 patients of the two arms having evaluable response, the clinical complete response rates to cisplatin were 14% and 22% and the complete plus partial response rates were 48% and 55% in the CTWS and in the AWS arm, respectively. These differences were not statistically significant. However, the survival curves were similar during the first 2 years but clearly diverged thereafter in favor of the AWS arm (p = 0.07). At 5 years, 12% and 30% of the patients were still alive in the CTWS and in the AWS arm, respectively. Hematologic toxicity was not relevant in either arm of the study. Nonhematologic toxicity, especially ototoxicity, was substantial and significantly higher in the AWS arm. Although statistically nonsignificant, this AWS regimen of cisplatin is associated with long-term better survival compared to the CTWS regimen in advanced ovarian carcinoma. This accelerated approach administering cisplatin should be further investigated, especially in patients with low residual disease after primary surgery.

Synthesis and structural characterization of 6I,6II-diamino-6I,6II-dideoxy-cyclomaltoheptaose, a difunctionalized beta-cyclodextrin.

6I,6II-Diamino-6I,6II-dideoxy-cyclomaltoheptaose was prepared using the regioselective procedure described by Tabushi. The difunctionalized beta-cyclodextrin crystallizes as hexadecahydrate in the orthorhombic space group P2(1)2(1)2(1), with a = 11.395(3), b = 32.989(9), c = 17.560(5) A, V = 6601 A3, Z = 4. The structure was solved by molecular replacement techniques using the program PATSEE and was refined to a conventional final R = 0.058 for the 5031 observed reflections with I > or = 3 sigma(I). The beta-CD macrocycle presents only slight differences with respect to uncomplexed hydrated or methylated beta-CD. The macrocycle structure maintains an approximate seven-fold symmetry. The round shape of the cyclodextrin ring is stabilized by intramolecular O-H ... O H-bonds between the secondary hydroxyl groups of neighbouring glucose residues. Along the a axis, the beta-CD molecules are arranged in columns; the macrocycles form a herring-bone pattern, so that the cavity of each beta-CD molecule is closed at each end by neighbouring molecules. The macrocycles are directly linked to each other by H-bonds involving either primary and secondary hydroxyl or amino groups of symmetry-related molecules. The resulting layers are connected to each other by a dense intermolecular hydrogen-bond network, in which solvent molecules participate.

Structural versatility of peptides containing C alpha, alpha-dialkylated glycines: conformational energy computations, i.r. absorption and 1H n.m.r. analysis of 1-aminocyclopropane-1-carboxylic acid homopeptides.

Conformational energy computations on the 1-aminocyclopropane-1-carboxylic acid mono-, di-, and tripeptide amides, Ac-(Ac3c)n-NHMe (n = 1-3), indicate that this C alpha, alpha-dialkylated, cyclic alpha-amino acid residue is conformally restricted and that type-I(I') beta-bends and distorted 3(10)-helices are particularly stable conformations for the di- and tripeptide amides, respectively. The results of the theoretical analysis are in agreement with those obtained in an i.r. absorption and 1H n.m.r. investigation in chloroform solution of Ac3c-rich tri- and tetrapeptide esters. A comparison is also made with the conclusions extracted from our previous work on peptides rich in Aib (alpha-aminoisobutyric acid), Ac5c (1-aminocyclopentane-1-carboxylic acid), and Ac6c (1-aminocyclohexane-1-carboxylic acid).

Structural versatility of peptides containing C alpha, alpha-dialkylated glycines. An X-ray diffraction study of six 1-aminocyclopropane-1-carboxylic acid rich peptides.

The molecular and crystal structures of six fully blocked, Ac3c-rich peptides to the tetramer level were determined by X-ray diffraction. The peptides are Fmoc-(Ac3c)2-OMe-CH3OH, Ac-(Ac3c)2-OMe, t-Boc-Ac3c-L-Phe-OMe, pBrBz-(Ac3c)3-OMe.H2O, Z-Gly-Ac3c-Gly-OTmb.(CH3)2CO, and t-Boc-(Ac3c)4-OMe.2H2O. Type-I (I') beta-bends and distorted 3(10)-helices were found to be typical of the tri- and tetrapeptides, respectively. In the dipeptides, too short to form beta-bend conformations, other less common structural features may be observed. The average geometry of the cyclopropyl moiety of the Ac3c residue is asymmetric and the N-C alpha-C' bond angle is significantly expanded from the regular tetrahedral value. A comparison with the structural preferences of other extensively investigated C alpha, alpha-dialylated alpha-amino acids is made and the implications for the use of the Ac3c residue in conformational design are examined.

Bone marrow biopsy in the staging of small cell lung cancer.

From April 1982 to December 1987, 71 patients with small cell lung cancer entered a randomized clinical trial, and underwent bone marrow biopsy (BMB) as part of staging procedures. We identified 8 patients (11%) with bone marrow metastases, 6 with extensive disease independently of BMB, and 2 with extensive disease on the basis of the BMB only. BMB determined a change in the stage in only 3% (2/71) of the cases. No differences were found in the hematological parameters of the patients with or without bone marrow metastases. The median survival of the patients with bone marrow involvement was the same (41 weeks) as those with extensive disease but without bone marrow involvement. We conclude that unilateral BMB without aspiration detects a substantial proportion of bone marrow metastases in patients with extensive disease. This fact does not worsen the prognosis. A small proportion of patients with apparently limited disease has bone marrow involvement. The technique therefore contributes, to a small extent, to the definition of the clinical stage of the disease. However, bone marrow involvement is an important data of natural history, and therefore new methods to better assess this peculiar site of the disease are needed.

Primary chemotherapy in operable breast carcinoma comparing CMF (cyclophosphamide, methotrexate, 5-fluorouracil) with an anthracycline-containing regimen: short-term responses translated into long-term outcomes.

BACKGROUND: The role of anthracyclines has been extensively studied in adjuvant chemotherapy, but much less in the primary chemotherapy of early breast carcinoma. This study, comparing CMF (cyclophosphamide, methotrexate, 5-fluorouracil) with the rotational anthracycline-containing regimen CMFEV (CMF plus epirubicin and vincristine) administered as primary chemotherapy, demonstrated a significant increase in clinical complete response in premenopausal women. We report the long-term results. PATIENTS AND METHODS: Two hundred and eleven patients with stage I or II palpable breast carcinoma and a tumour diameter of >2.5 cm were randomised to receive CMF or CMFEV for four cycles before surgery. After surgery, the patients in both arms received adjuvant CMF for three cycles. RESULTS: In the study population as a whole, there was a non-significant 20% reduction in mortality and relapse rates in the CMFEV arm. However, the effect of the experimental regimen was only found in premenopausal patients, especially in terms of relapse-free survival (P=0.07) and locoregional relapse-free survival (P=0.0009), thus mirroring the effect on response rates. After 10 years, the proportions of premenopausal patients free from locoregional relapse as a first event in the CMF and CMFEV groups were 68% and 97%, respectively. No relevant differences were found in postmenopausal patients. CONCLUSION: The overall results of this study showed that the greater activity of the experimental anthracycline-containing combination over CMF as primary chemotherapy in premenopausal patients translated into long-term effects in the same subgroup.

Randomized comparison of 5-FU alone or combined with mitomycin and cytarabine (MFC) in the treatment of advanced gastric cancer.

In a prospective randomized study, 53 patients with advanced gastric cancer previously untreated by chemotherapy were randomly assigned to treatment with 5-FU alone or combined with mitomycin and cytarabine (MFC). The response rate with MFC was higher (28%) than with 5-FU alone (21%). The difference, however, was not statistically significant. Median response duration was practically identical with 5-FU (16 weeks) and MFC (17 weeks). There was no difference in median survival between the two groups (39 and 43 weeks, respectively).

Noncoded residues as building blocks in the design of specific secondary structures: symmetrically disubstituted glycines and beta-alanine.

Structural changes can be induced in a peptide by selective substitution of coded alpha-amino acid residues by noncoded alpha-amino acid residues and the consequent production of analogues with modified structure and conformational preferences. In this review article we summarize the solid state structural results and the conformational preferences of two classes of "building blocks": (a) the linear and cyclic symmetrically alpha, alpha-disubstituted glycines in which either two identical n-alkyl groups replace the hydrogen atoms of the glycine residue or a cyclic aliphatic side-chain system is formed by linking the two alpha-carbon side chains, respectively; and (b) the beta-alanine residue. Examples, whenever possible, of the use of these residues for the elucidation of the bioactive conformation in the appropriate biological systems will be given.

[Aib5,6-D-Ala8]-cyclolinopeptide A, grown from a benzene/acetonitrile mixture.

cyclo-(Prolyl-prolyl-phenylalanyl-phenylalanyl- alpha-aminoisobutyryl-alpha-aminoisobutyryl-isoleucyl-D-alan yl-valyl) ([Aib5,6-D-Ala8]-cyclolinopeptide A), grown from benzene/acetonitrile mixture, crystallizes with one acetonitrile and two water molecules. The molecular structure is almost identical to that obtained from methanol/water. The dimension of the solvent channels found in these structures is reduced in the present one, but the intramolecular hydrogen-bond pattern is preserved. The Pro1-Pro2 peptide unit is cis (omega = 8 degrees); all others are trans.

Structure of N-acetyl-D-alanyl-D-alanine hydrate. An analogue of the COOH-terminal segment of peptidoglycan of bacterial cell walls.

The solid state conformational analysis of Ac-D-Ala-D-Ala-OH.H2O, carried out by infrared absorption and X-ray diffraction, has indicated that the molecules are not extended in a regular beta conformation, but rather that they are partially folded, the phi, psi torsional angles of the COOH-terminal residue in particular being in the region of the left-handed alpha helix of the Ramachandran map. The acetylamino and peptide groups ar found in the usual trans conformation, the latter, however, exhibiting a deviation from rigid planarity. Only intermolecular hydrogen bonds occur in the crystal state. The solution conformational analysis, performed by infrared absorption and CD, has revealed that the amount of intramolecular N--H ... O==C hydrogen-bonded folded forms, if any, should be extremely small, even in deuteriochloroform at high dilution. In water, solvated, unordered species largely predominate.

beta-Alanyl-beta-alanine in cyclic beta-turned peptides.

In the present paper we describe the synthesis, purification, and single crystal x-ray analysis of the cyclic pentapeptide cyclo-(L-Pro-L-Pro-L-Phe-beta-Ala-beta-Ala). The peptide was synthesized by classical solution methods and the cyclization of the free pentapeptide was accomplished in good yields in diluted methylene-chloride solution using N,N-dicyclohexylcarbodiimide. The compound crystallizes in the monoclinic space group P21 from hot water with five solvent molecules. The Pro1-Pro2 peptide bond is cis and the molecular conformation is stabilized by an intramolecular hydrogen bond between the CO group of the beta-Ala5 and the NH of the Phe3 residue. The Pro1-Pro2 segment occupies the relative positions 2 and 3 of a type VIa beta-turn, while the L-phenylalanyl-beta-alanyl-beta-alanine segment is incorporated in a C13-like ring structure. The crystal packing is characterized by a network of 11 intermolecular hydrogen bonds involving all the remaining CO, NH, and the water molecules.

Cisplatin and etoposide in advanced colorectal carcinoma.

The cisplatin (P) and etoposide (E) combination has been found to be active in several types of solid tumors. It has never been previously tested in advanced colorectal cancer. Thirty-three patients with advanced colorectal cancer were treated with this combination. Five patients responded (1 complete and 4 partial responses) with an overall response rate of 15% (95% confidence limits, 3%-27%). Responses were seen in both untreated (3/16) and pretreated (2/17) patients. The median duration of response was 28 weeks (range: 23; 80), the median time to progression was 16 weeks (range 2; 80) and the median survival time for all entered patients was 38 weeks (range: 2; 187+). These results suggest that the PE combination has a low but definite activity in advanced colorectal carcinoma, particularly in previously untreated patients.

Structure-toxicity relationships in the amatoxin series. Synthesis of S-deoxy[gamma(R)-hydroxy-Ile3]-amaninamide, its crystal and molecular structure and inhibitory efficiency.

The amatoxins, highly toxic components of Amanita mushrooms, strongly inhibit the DNA-dependent RNA polymerase II (or B) in eukaryotic cell nuclei. For optimal binding to the enzyme a gamma-hydroxyisoleucine side chain in the 3-position is important as in gamma-amanitin (compound 1), where the OH-group is bound in the [S]-configuration. Amanullin, a non-toxic component, having an oxygen-free isoleucine side chain no. 3, exhibits an inhibitory effect on RNA polymerase II about two orders of magnitude smaller than that of gamma-amanitin. An equal, relatively weak, inhibitory effect has previously been found with the synthetically obtained Ile3-analog 7. In the present paper the synthesis of an analog (2) bearing a gamma-hydroxyl group in the isoleucine side chain is described. The compound was found to have about the same inhibitory effect on RNA polymerase II from Drosophila embryos as amanullin and the Ile3-analog 7. Structure analysis by X-ray diffraction revealed that the hydroxyl group at the -carbon atom of side chain-3 has the [R]-configuration, the new analog thus being -deoxo[( )-hydroxy-[Ile3]-amaninamide. It follows that the [S]-configuration of this chiral center is a prerequisite to maximal toxicity. Crystallographic data demonstrating great similarity between the peptide backbones of the new analog and those of natural amatoxins are given.