New onset atrial fibrillation in STEMI patients: main prognostic factors and clinical outcome

Background

New onset atrial fibrillation (NOAF) is not a so rare condition among patients hospitalized for ST-segment elevation myocardial infarction (STEMI). Several studies showed that NOAF during an acute coronary syndrome (ACS) leads to increased mortality, both at short and long term. The indications for the treatment of patients with known AF undergoing percutaneous coronary interventions (PCI) are clear, while less is available about the management of NOAF during ACS and in particular during STEMI. The purpose of this study is therefore to evaluate mortality and clinical outcome of this high risk subgroup of patients.

Methods

We analysed 1455 consecutive patients undergoing coronary angiography and/or PCI for STEMI. CHA2DS2-VASc and HAS-BLED scores were calculated for all patients. In-hospital, 1-year and long-term follow up mortality was evaluated for all patients. Cerebral ischemic and hemorrhagic events were also evaluated as clinical endpoints at 1 year.

Results

NOAF was detected in 102 subjects, 62.7% males, with a mean age of 74.8±10.6 years. We found a high prevalence of main cardiovascular risk factors such as hypertension, dyslipidemia, smoke and renal failure. Mean ejection fraction (EF) was 43.5±12.1% and the mean atrial volume was increased (58±20.9 ml). The most represented type of MI at admission was anterior STEMI (46%). NOAF occurred mainly in the peri-acute phase and had a very variable duration (8.1±12.5 min). During hospitalization all patients were treated with Enoxaparin, but only 25.2% of them were discharged with long term oral anticoagulation (16.7% warfarin, 4.9% direct oral anticoagulant). The majority of patients had a CHA2DS2-VASc score >2 and a HAS-BLED score of 2 or 3. In-hospital mortality was 14.2%, while 1-year mortality was 17.2% and long term mortality 32.1% (median follow-up time 1820 days, range 341 to 3985). Through a logistic regression analysis we identified age as an independent predictor of mortality both at short and long term follow up, while EF was the only independent predictor for in-hospital mortality and arrhythmia duration for 1-year mortality. At 1-year follow up we recorded three ischemic strokes, while no bleeding complications.

Conclusions

STEMI patients who develop NOAF are a very high-risk population and are characterized by increased short and long term mortality. NOAF should be diagnosed and treated as soon as possible with a correct indication to long term OAC based on the ratio between ischemic and hemorrhagic risk.

Funding Acknowledgement

Type of funding sources: None.

P1515 Hemodynamic determinants of tricuspid annular pulmonary systolic excursion (TAPSE)/ systolic pulmonary arterial pressure (SPAP) ratio in Heart Failure with reduced Ejection Fraction

Background

the TAPSE/SPAP ratio has gained a role as an easy-to-use surrogate of right ventricle-to-pulmonary circulation (RV-PC) coupling, showing a strong prognostic significance in heart failure (HF) patients. The hemodynamic determinants of TAPSE/SPAP ratio, as assessed by invasive approach, have not been fully clarified.

Aim

To identify the right heart hemodynamic variables correlated with TAPSE/SPAP in a HF with reduced EF (HFrEF) cohort, both at rest and during exercise.

Methods

30 HFrEF patients (age 68 ± 10 years LV EF 28 ± 7) underwent to rest and exercise echocardiography and performed right heart catheterization within 24 hours. Bivariate correlations between TAPSE/SPAP ratio (at rest and during exercise), right heart hemodynamic variables, RV systolic function and NTproBNP have been explored.

Results

TAPSE/SPAP ratio at rest showed a moderate correlation with pulmonary artery wedge pressure (PAWP: r= 0.441; p= 0.039), pulmonary artery pressures (PAP systolic: r = 0.481; p= 0.026; PAP diastolic: r= 0.434; p= 0.043; mPAP: r= 0.476; p= 0.025), pulmonary vascular resistance and compliance (r= 0.475; p= 0.041). A stronger correlation was identified with right atrial (RAP systolic: r= 0.586; p= 0.017; RAP diastolic: r= 0.681; p= 0.006) and right ventricular pressures- in particular diastolic ones (RVP systolic: r= 0.584; p= 0.004; RAP diastolic: r= 0.652; p= 0.002). No significant correlation with NTproBNP and RV 3D EF emerged. Exercise TAPSE/SPAP ratio significantly correlated with right atrium (RAP systolic: r= 0.564; p= 0.036) and right ventricle systolic pressures only (RVP systolic: r= 0.789; p< 0.001).

Conclusions

TAPSE/SPAP ratio at rest showed a stronger correlation with invasively derived diastolic right heart pressure rather than pulmonary vascular bed pressures. A similar correlation was also observed for exercise TAPSE/SPAP ratio. This tight correlation with RV, rather than with vascular pressures, supports the significance of this ratio as a marker of RV adaptation to vascular overload.

4306Hemodynamic correlates of tricuspid annular pulmonary systolic excursion (TAPSE)/systolic pulmonary arterial pressure (SPAP) ratio in heart failure with reduced ejection fraction

Background

The TAPSE/SPAP ratio has gained a role as an easy-to-use surrogate of right ventricle-to-pulmonary circulation (RV-PC) coupling, showing a strong prognostic significance in heart failure (HF) patients. The hemodynamic determinants of TAPSE/SPAP ratio, as assessed by invasive approach, have not been fully elucidated.

Aim

To identify the right heart hemodynamic variables correlated with TAPSE/SPAP in a HF with reduced EF (HFrEF) cohort, at rest and during exercise.

Methods

24 HFrEF patients (age 67±11 years LV EF 27±7) underwent to rest and exercise echocardiography and performed right heart catheterization within 24 hours. Bivariate correlations between TAPSE/SPAP ratio (at rest and exercise), right heart hemodynamic variables, RV systolic function and NTproBNP have been explored.

Results

TAPSE/SPAP ratio at rest showed a moderate correlation with pulmonary artery wedge pressure (PAWP: r=0.432; p=0.039), pulmonary artery pressures (PAP systolic: r=0.474; p=0.026; PAP diastolic: r=0.434; p=0.043; mPAP: r=0.476; p=0.025), pulmonary vascular resistance and compliance (r=0.475; p=0.041), while a stronger correlation was identified with right atrial (RAP systolic: r=0.571; p=0.017; RAP diastolic: r=0.675; p=0.006) and right ventricular pressures- in particular diastolic ones (RVP systolic: r=0.584; p=0.004; RAP diastolic: r=0.646; p=0.002). No significant correlation was found with NTproBNP and RV 3D EF. Exercise TAPSE/SPAP ratio significantly correlated with right atrium (RAP systolic: r=0.564; p=0.036) and right ventricle systolic pressures only (RVP systolic: r=0.765; p<0.001).

TAPSE/PAPS correlation graphics

Conclusions

TAPSE/SPAP ratio at rest showed a stronger correlation with invasively derived diastolic right heart pressure rather than pulmonary vascular bed pressures. A similar correlation was also observed for exercise TAPSE/SPAP ratio. This tight correlation with RV, rather than vascular pressures, supports the significance of the ratio as a marker of RV adaptation to vascular overload.

NIR Emitting Nanoprobes Based on Cyclic RGD Motif Conjugated PbS Quantum Dots for Integrin-Targeted Optical Bioimaging

Here, silica-coated PbS quantum dots (QDs) with photoluminescence emission properties in the near-infrared (NIR) region are proposed as potential effective single particle optical nanoprobes for future in vivo imaging of tumors. The dispersibility in aqueous medium of hydrophobic PbS QDs was accomplished by growing a silica shell on their surface by exploiting a base assisted water-in-oil microemulsion method. The silica-coated PbS QDs were then conjugated with a specifically designed cyclic arginine-glycine-aspartic acid (cRGD) peptide that is able to specifically recognize αvβ3 integrins, which are overexpressed in angiogenic tumor-induced vasculatures and on some solid tumors, to achieve tumor-specific targeting. The cRGD peptide PbS silica-coated QDs were systematically characterized, at each step of their preparation, by means of complementary optical and structural techniques, demonstrating appropriate colloidal stability and the maintenance of their optical futures in aqueous solutions. The cellular uptake of cRGD peptide functionalized luminescent nanostructures in human melanoma cells, where overexpression of αvβ3 was observed, was assessed by means of confocal microscopy analysis and cytometric study. The selectivity of the cRGD peptide PbS silica-coated QDs for the αvβ3 integrin was established, consequently highlighting the significant potential of the developed NIR emitting nanostructures as optically traceable nanoprobes for future αvβ3 integrin receptor in vivo targeting in the NIR region.

Silver nanoparticles functionalized with a fluorescent cyclic RGD peptide: a versatile integrin targeting platform for cells and bacteria

A green fluorescent RGD peptide–silver nanoparticle platform to target integrin receptors in cells and bacterial studies.

Determination of the secondary structure of peptides in the presence of Gram positive bacterium S. epidermidis cells

Temporin L folds into α helix upon incubation with S. epidermidis cells.

Evidences of complex formation between DABA-based nucleo-gamma-peptides with alternate configuration backbone

In the present work, we report the synthesis and the characterization of dab PNA hexamers with diaminobutyric acid backbone of D- or/and L-configuration. In particular, the four nucleo-amino acids we synthesized, D- and L-diaminobutyryl adenines and D- and L-diaminobutyryl thymines, were used in various combinations to assemble the following oligomers: H-G-(t( L-dab))(6)-K-NH(2), H-G-(t( D-dab))(6)-K-NH(2), H-G-(a( L-dab))(6)-K-NH(2), H-G-(t( L-dab)-t( D-dab))(3)-K-NH(2), H-G-(a( L-dab)-a( D-dab))(3)-K-NH(2), H-G-(a( L-dab)-t( D-dab))(3)-K-NH(2). By using CD and UV spectroscopies, we investigated the ability of complementary dab PNA strands to bind to each other. We found that binding occurs only between oligomers with backbone of alternate configuration [(t( L-dab)-t( D-dab))(3)/(a( L-dab)-a( D-dab))(3) and (a( L-dab)-t( D-dab))(3)/(a( L-dab)-t( D-dab))(3)] and implies cooperative hydrogen bonds and base stacking. Furthermore, interesting properties relative to the self-complementary oligomer (a( L-dab)-t( D-dab))(3) forming palindromic complexes emerged from preliminary dynamic light-scattering experiments that suggested the formation of multimeric aggregates. These results, together with the high serum stability of the DABA-based oligomers, as shown by HPLC analysis, encourage us to further study dab PNAs as new self-recognizing bio-inspired polymers, to develop new nanomaterials in biotechnological and biomedical applications.

Laparoscopic treatment of paraesophageal and mixed diaphragmatic hernias. Report of two cases

Hiatal hernias are classified into 3 types: sliding hernia (type I), paraesophageal hernia (type II) and mixed hernia (type III), that is a combination of type I and II. The paraesophageal and mixed hernias represent about 5-10% of the surgically treated hiatal hernias. The surgical treatment of the paraesophageal and mixed hernias is unavoidable because of the high risk of severe complications and it has to be considered in a high percentage of cases. The most important technical difficulty in the video-laparoscopic treatment is represented by the hugeness of the hernial defect and by the challenging reduction of the stomach into the abdomen. A cautious dissection of hernial sac and diaphragmatic cruses as well as a careful crural repair make the video-laparoscopic procedure feasible. The operative times are not prolonged and the results are similar to the open technique ones. In literature, the incidence of both intra and postoperative complications doesn't exhibit statistically significant differences between laparoscopic and open techniques. Because of the complexity of the laparoscopic procedure, the minimally invasive access has to be reserved to surgeons who are well trained in those techniques. In this paper we describe 2 cases: one of paraesophageal hernia and the other of mixed hernia which were video-laparoscopically treated with the help, in the second case, of a Gore-Tex mesh. In both cases the technical results were positive. Intra and postoperative complications didn't occur and, one year after the surgical procedure, both patients were in good health and recurrence-free.

Sutureless and stapleless laparoscopic splenectomy using radiofrequency: LigaSure device

BACKGROUND

Bleeding is the main complication and cause of conversion during laparoscopic splenectomy (LS). We present the advantages of the LigaSure vessel sealing system added to the lateral approach for achieving safe vascular control.

METHODS

We performed 63 consecutive LS in a 3-year period using LigaSure in two affiliated university hospitals. We employed a right semilateral position technique with dissection of the spleen and vessel sealing using LigaSure. Forty-two patients had benign hematological disease, 19 had malignant disease, and two had splenic cysts.

RESULTS

A total of 58 LS were completed with five conversions due to hilar bleeding (three cases), difficult dissection (one), and massive splenomegaly (one). In all but five patients, blood loss was less than 100 ml. No transfusions were needed. There were five postoperative complications: portal thrombosis (one case), hemoperitoneum (two), surgical wound infection (one), and pleural effusion (one).

CONCLUSIONS

The use of LigaSure, and the semilateral position, results in a gain of time and safety. Furthermore, average intraoperative bleeding is very low.

Conformational analysis by NMR and distance geometry techniques of a peptide mimetic of the third helix of the Antennapedia homeodomain

The Antennapedia homeodomain structure consists of four helices. The helices II and III are connected by a tripeptide that forms a turn, and constitute the well-known helix-turn-helix motif. The recognition helix penetrates the DNA major groove, gives specific protein-DNA contacts and forms direct, or water-mediated, intermolecular hydrogen bonds. It was suggested that helix III (and perhaps also helix IV) might represent the recognition helix of Antennapedia homeodomain, which makes contact with the surface of the major groove of the DNA. In an attempt to clarify the helix III capabilities of assuming an helical conformation when separated from the rest of the protein, we carried out the structural determination of the recognition helix III in different solvent media. The conformational study of fragments 42-53, where residues W48 and F49, not involved in the protein-DNA interaction, were substituted by two alanines, was conducted in sodium dodecyl sulfate (SDS), trifluoroethanol (TFE) and TFE/water, using circular dichroism, nuclear magnetic resonance (NMR) and distance geometry (DG) techniques. The fragment assumes a well-defined secondary structure in TFE and in TFE/water (90/10, v/v) with an alpha-helix encompassing residues 4-9, while in TFE/water (70/30, v/v) a less regular structure was found. The DG results in the micellar system evidence the presence of a distorted alpha-helical conformation involving residues 4-8. Our results reveal that the isolated Antennapedia recognition helix III tend to preserve in solution the alpha-helical conformation even if separated from the rest of the molecule.

Peptide nucleic acids (PNA)-DNA chimeras targeting transcription factors as a tool to modify gene expression

Peptide nucleic acids (PNAs)-DNA chimeras have been recently described as DNA mimics constituted of a part of PNA and of a part of DNA. We have demonstrated that double stranded molecules based on PNA-DNA chimeras bind to transcription factors in a sequence-dependent manner. Accordingly, these molecules can be used for transcription factor decoy (TFD) pharmacotherapy. Effects of double stranded PNA-DNA chimeras targeting NF-kappaB and Sp1 were determined on in vitro cultured human cells and were found to be comparable to those observed using double-stranded DNA decoys. The TFD molecules based on PNA-DNA chimeras can be further engineered by addition of short peptides facilitating cell penetration and nuclear localization. Therefore, these engineered molecules could be of great interest for in vivo experiments for non-viral gene therapy of a variety of diseases, including neoplastic and viral diseases, for which the TFD approach has been already demonstrated as a very useful strategy.

[Four cases of mesenteric cystic neoformations]

Four cases of mesenteric cystic neoformations personally observed in the last years are reported. This pathology should not be underestimated, since not only does it present several problems regarding diagnosis and treatment, but a nosologic classification is also difficult to make. Since such cysts present with aspecific symptoms, a definite diagnosis cannot always be reached by a preliminary X-ray investigation, which may lead to various interpretations, but often requires a subsequent histologic examination of operative specimen.

[Adenocarcinoma of pancreas with situs viscerum inversus totalis]

A case of adenocarcinoma of the head of the pancreas in a patient with situs viscerum inversus totalis, an association described for the third time in literature, is reported. The possible coexistence of malformations of transposed organs and the specular anatomosurgical situation requires particular attention in the diagnosis and preoperative evaluation as well as a careful reorientation of the surgical perspective and a correct surgical conduct.

[Giant ovarian cyst. A case weighing 23 kg (50.6 lb). Literature review]

The ovarian cysts are one of the most common affections for females. Besides non-neoplastic functional cysts (follicular or luteal) with relatively small sizes, the neoplastic types, generally benign and that can be ascribed to serous tumors, of 10-15 cm or even bigger should be included. Nowdays, these neoformations are diagnosed relatively early, before they become of big dimensions, even if often they present few symptoms. Then it seems to be interesting to report a case recently observed of an ovarian cyst of 35x45x50 cm and weighing 23 kg in 29-year-old woman.

Crystal structure of the W35A mutant thioredoxin h from Chlamydomonas reinhardtii: the substitution of the conserved active site Trp leads to modifications in the environment of the two catalytic cysteines

The conformational analysis of W35A thioredoxin h from the eukaryotic green alga Chlamydomonas reinhardtii in the solid state has been carried out by x-ray diffraction, with the aim to clarify the role of Trp in the catalysis. Comparative analysis of W35A mutant with wild-type (WT) thioredoxin shows that, even if the structural motif of thioredoxin is not perturbed, the substitution of Trp35 by an Ala leads to significant changes in protein conformation near the active site. This rearrangement increases its solvent exposure and explains the change of the pKa values of the catalytic cysteines. The substitution of the Trp residue also influences the crystal packing as well as the recognition ability of thioredoxin. The solid state analysis suggests that the Trp residue has a structural function both to force the active site in the bioactive conformation, and to mediate the protein-protein recognition.

Molecular interactions with nuclear factor kappaB (NF-kappaB) transcription factors of a PNA-DNA chimera mimicking NF-kappaB binding sites

The decoy approach against nuclear factor kappaB (NF-kappaB) is a useful tool to alter NF-kappaB dependent gene expression using synthetic oligonucleotides (ODNs) carrying NF-kappaB specific cis-elements. Unfortunately, ODNs are not stable and need to be be extensively modified to be used in vivo or ex vivo. We have previously evaluated the possible use of peptide nucleic acids (PNAs) as decoy molecules. The backbone of PNAs is composed of N-(2-aminoethyl)glycine units, rendering these molecules resistant to both nucleases and proteases. We found that the binding of NF-kappaB transcription factors to PNAs was either very low (binding to PNA-PNA hybrids) or exhibited low stability (binding to PNA-DNA hybrids). The main consideration of the present paper was to determine whether PNA-DNA chimeras mimicking NF-kappaB binding sites are capable of stable interactions with proteins belonging to the NF-kappaB family. Molecular modeling was employed for the design of PNA-DNA chimeras; prediction of molecular interactions between chimeras and NF-kappaB nuclear proteins were investigated by molecular dynamics simulations, and interactions between PNA-DNA chimeras and NF-kappaB proteins were studied by gel shifts. We found significant differences between the structure of duplex NF-kappaB PNA-DNA chimera and duplex NF-kappaB DNA-DNA. However, it was found that these differences do not prevent the duplex PNA-DNA chimera from binding to NF-kappaB transcription factors, being able to suppress the molecular interactions between HIV-1 LTR and p50, p52 and nuclear factors from B-lymphoid cells. Therefore, these results demonstrate that the designed NF-kappaB DNA-PNA chimeras could be used for a decoy approach in gene therapy.

Crystal structure of the wild-type and D30A mutant thioredoxin h of Chlamydomonas reinhardtii and implications for the catalytic mechanism

Thioredoxins are ubiquitous proteins which catalyse the reduction of disulphide bridges on target proteins. The catalytic mechanism proceeds via a mixed disulphide intermediate whose breakdown should be enhanced by the involvement of a conserved buried residue, Asp-30, as a base catalyst towards residue Cys-39. We report here the crystal structure of wild-type and D30A mutant thioredoxin h from Chlamydomonas reinhardtii, which constitutes the first crystal structure of a cytosolic thioredoxin isolated from a eukaryotic plant organism. The role of residue Asp-30 in catalysis has been revisited since the distance between the carboxylate OD1 of Asp-30 and the sulphur SG of Cys-39 is too great to support the hypothesis of direct proton transfer. A careful analysis of all available crystal structures reveals that the relative positioning of residues Asp-30 and Cys-39 as well as hydrophobic contacts in the vicinity of residue Asp-30 do not allow a conformational change sufficient to bring the two residues close enough for a direct proton transfer. This suggests that protonation/deprotonation of Cys-39 should be mediated by a water molecule. Molecular-dynamics simulations, carried out either in vacuo or in water, as well as proton-inventory experiments, support this hypothesis. The results are discussed with respect to biochemical and structural data.

Synthesis and solution characterization of a porphyrin-CCK8 conjugate

In this paper we report the synthesis and a detailed NMR solution characterization of a new CCK8 analogue and its indium(III) complex, PK-CCK8 and In-PK-CCK8. The new compounds contain a porphyrin moiety covalently bound through an amide bond to the side chain of a Lys residue introduced at the N-terminus of CCK8. A molecular dynamics simulation, based on the NMR structure of the complex between CCK8 and the N-terminal extracellular arm of the CCK(A) receptor, is also reported. Both the NMR study and the molecular dynamics simulation indicate that the porphyrin-peptide conjugate might be able to bind to the CCK(A) receptor model. The results of the molecular dynamics calculations show that the conformational features of the CCK8/CCK(A) receptor model complex and of the PK-CCK8/CCK(A) receptor-model complex are similar. This evidence supports the view that the introduction of the porphyrin-Lys moiety does not influence the mode of ligand binding to the CCK(A) receptor model. The NMR structure of PK-CCK8 in DMSO consists of a well defined pseudo-helical N-terminal region, while the C-terminal region is flexible. Moreover, the absence of NOE contacts between the porphyrin and the peptide indicates that the macrocyclic ring is directed away from the peptide region involved in the binding with the receptor.

Structural and kinetic characterization of native laccases from Pleurotus ostreatus, Rigidoporus lignosus, and Trametes trogii

A comparative study has been performed on five native laccases purified from the three basidiomycete fungi Pleurotus ostreatus, Rigidoporus lignosus, and Trametes trogii to relate their different catalytic capacities to their structural properties. Spectroscopic absorption features and EPR spectra at various pH values of the five enzymes are very similar and typical of the blue oxidases. The analysis of the dependence of kinetic parameters on pH suggested that a histidine residue is involved in the binding of nonphenolic substrates, whereas both a histidine and an acidic residue may be involved in the binding of phenolic compounds. His and an Asp residue are indeed found at the bottom of a cavity which may be regarded as a suitable substrate channel for approaching to type 1 copper in the 3D homology models of the two laccases from Pleuorotus ostreatus (POXC and POXAlb) whose sequences are known.

[Surgical treatment of hemorrhoidal disease using the circular stapler. Analysis of 60 operated cases]

BACKGROUND

The authors describe their experience of the treatment of hemorrhoidal disease using a circular stapler in order to evaluate the effectiveness of this technique.

METHODS

They describe the surgical technique used in a comparative study carried out at Modena Policlinic. A transversal mucohemorrhoidal transection is performed using a circular stapler above the anorectal joint, enabling radical surgery to be completed in a single stage with a rapid and mini-invasive technique. This technique associates the resection of hemorrhoidal nodules and prolapsed mucosa with fixing the residual mucosa to the anal canal and correcting the hypertension and hematic stasis in the venous spaces by breaking the terminal branches of the superior hemorrhoidal artery. Both male and female patients were enrolled in the study, aged over 18 years old, presenting second, third and fourth degree hemorrhoidal prolapse with indications for surgery. The analysis of the long-term follow-up for possible late complications in the 60 selected cases will be reported in a later work.

RESULTS

The technique is easy, rapid and causes moderate pain. The postoperative complications are negligible.

CONCLUSIONS

A hospital stay limited to a few hours, rapid physical recovery and the absence of out-patient treatment required by this surgical technique, which is comparable to an internal closed hemorrhoidectomy, all offer undoubted advantages, also of a psychological and social nature which amply justify the higher economic and management cost linked to the use of a surgical stapler.

Solid state and solution conformation of [Ala7]-phalloidin: a synthetic phallotoxin analogue

Phallotoxins are toxic compounds produced by poisonous mushroom Amanita phalloides and belong to the class of bicyclic peptides with a transannular thioether bridge. Their intoxication mechanism in the liver involves a specific binding of the toxins to F-actin that, consequently, prevents the depolymerization equilibrium with G-actin. Even though the conformational features of phallotoxins have been worked out in solution, the exact mechanism of interaction with F-actin is still unknown. In this study a toxic phalloidin synthetic derivative, bicyclo(Ala1-D-Thr2-Cys3-cis-4-hydroxy-Pro4-Ala5-2-mercapto-Trp6-Ala7)(S-3-->6) has been synthesized. A substitution at position 7. with an Ala residue replaces the 4,5-dihydroxy-Leu present in the natural phalloidin. This analogue has formed crystals suitable for X-ray analysis, and represents the first case for such a class of compounds. The solid-state structure as well as the solution conformation have been evaluated. NMR techniques have been used to extract interproton distances as restraints in subsequent molecular dynamics calculations. Finally, a direct comparison between structures in solution and in the solid state is presented.

Ac10c: a medium-ring, cycloaliphatic Calpha,alpha-disubstituted glycine. Incorporation into model peptides and preferred conformation

Two complete series of N-protected oligopeptide esters to the pentamer level from 1-amino-cyclodecane-1-carboxylic acid (Ac10c), an alpha-amino acid conformationally constrained through a medium-ring Calphai <--> Calphai cyclization, and either the L-Ala or Aib residue, along with the N-protected Ac10c monomer and homo-dimer alkylamides, were synthesized using solution methods and fully characterized. The preferred conformation of these model peptides was assessed in deuterochloroform solution using FT-IR absorption and 1H NMR techniques. Furthermore, the molecular structures of two derivatives (Z-Ac10c-OH and Fmoc-Ac10c-OH) and two peptides (the dipeptide ester Z-Ac10c-L-Phe-OMe and the tripeptide ester Z-Aib-Ac10c-Aib-OtBu) were determined in the crystal state using X-ray diffraction. The experimental results support the view that beta-bends and 3(10)-helices are preferentially adopted by peptides rich in Ac10c, the third largest cycloaliphatic C(alpha,alpha)-disubstituted glycine known. This investigation allowed us to complete a detailed conformational analysis of the whole 1-amino-cycloalkane-1-carboxylic acid (Ac(n)c, with n = 3-12) series, which represents the prerequisite for our recent proposal of the 'Ac(n)c scan' concept.

A single point mutation (Glu85Arg) increases the stability of the thioredoxin from Escherichia coli

Glu85 in the Escherichia coli thioredoxin, which is localized in the loop between beta4 and beta5, was substituted with the Arg present in the corresponding position in Bacillus acidocaldarius thioredoxin. This suggested that it could play an important role in the structure and thermostability of this protein owing to its involvement in numerous interactions. The effects of the mutation on the biophysical properties were analysed by circular dichroism, spectrofluorimetry and limited proteolysis, supported by molecular dynamics data. As modelling predicted, an increase in stability for E85R due to additional H-bonds between the beta5 and alpha4 regions was observed.

Structural consequences of metal complexation of cyclo[Pro-Phe-Phe-Ala-Xaa]2 decapeptides

The conformational features of both free and Ca2+-complexed cyclo[Pro-Phe-Phe-Ala-Xaa]2 (with Xaa= Glu(OtBu), Lys(CIZ), Leu, and Ala) in solution have been determined by NMR spectroscopy and extensive distance-geometry calculations. The decapeptides are conformationally homogeneous in solution and show common structural features in their free and complexed forms. The structures of the free form contain only trans peptide bonds and are topologically similar to the structure of gramicidin-S, folded up in two antiparallel extended structures, stabilized by interstrand hydrogen bonds, and closed at both ends by two beta-turns. In contrast, the Ca2+-complexed peptides present two cis peptide bonds and are generally similar to those observed for the metal-complexed forms of antamanide and related analogues, folded into a saddle shape with two beta-turns. The Glu(OtBu)-, Leu-, and Lys(ClZ)-containing peptides examined here maintain the biological activity of the cyclolinopeptide A in their ability to competitively inhibit cholate uptake. The natural antamanide and cyclolinopeptide A are both able to inhibit the uptake of bile salts into hepatocytes. They share the same postulated active sequence Pro-Phe-Phe. Based on our structural results, we conclude that the ability to adopt a global conformation, characterized by a clear amphipathic separation of hydrophobic and hydrophilic surfaces, is an important feature for the functioning of this class of peptides.

Crystal-state conformation of Calpha,alpha-dialkylated peptides containing chiral beta-homo-residues

Secondary structure formation and stability are essential features in the knowledge of complex folding topology of biomolecules. To better understand the relationships between preferred conformations and functional properties of beta-homo-amino acids, the synthesis and conformational characterization by X-ray diffraction analysis of peptides containing conformationally constrained Calpha,alpha-dialkylated amino acid residues, such as alpha-aminoisobutyric acid or 1-aminocyclohexane-1-carboxylic acid and a single beta-homoamino acid, differently displaced along the peptide sequence have been carried out. The peptides investigated are: Boc-betaHLeu-(Ac6c)2-OMe, Boc-Ac6c-betaHLeu-(Ac6c)2-OMe and Boc-betaHVal-(Aib)5-OtBu, together with the C-protected beta-homo-residue HCl.H-betaHVal-OMe. The results indicate that the insertion of a betaH-residue at position 1 or 2 of peptides containing strong helix-inducing, bulky Calpha,alpha-disubstituted amino acid residues does not induce any specific conformational preferences. In the crystal state, most of the NH groups of beta-homo residues of tri- and tetrapeptides are not involved in intramolecular hydrogen bonds, thus failing to achieve helical structures similar to those of peptides exclusively constituted of Calpha,alpha-disubstituted amino acid residues. However, by repeating the structural motifs observed in the molecules investigated, a beta-pleated sheet secondary structure, and a new helical structure, named (14/15)-helix, were generated, corresponding to calculated minimum-energy conformations. Our findings, as well as literature data, strongly indicate that conformations of betaH-residues, with the micro torsion angle equal to -60 degrees, are very unlikely.

Computational procedures to explain the different biological activity of DNA/DNA, DNA/PNA and PNA/PNA hybrid molecules mimicking NF-kappaB binding sites

Peptide nucleic acids (PNA) have recently been proposed as alternative reagents in experiments aimed to the control of gene expression. In PNAs, the pseudopeptide backbone is composed of N-(2-aminoethyl)glycine units and therefore is stable in human serum and cellular extracts. PNAs hybridize with high affinity to complementary sequences of single-stranded RNA and DNA, forming Watson-Crick double helices and giving rise to highly stable (PNA)2-RNA triplexes with RNA targets. Therefore, antisense and antigene PNAs have been synthetized and characterized. The major issue of the present paper is to describe some computational procedures useful to compare the behaviour of PNA double stranded molecules and PNA/DNA hybrids with the behaviour of regular DNA duplexes in generating complexes with DNA-binding proteins. The performed computational analyses clearly allow to predict that the lack of charged phosphate groups and the different shape of helix play a critical role in the binding efficiency of NF-kappaB transcription factors. These computational analyses are in agreement with competitive gel shift and UV-cross linking experiments. These experiments demonstrate that NF-kappaB PNA/PNA hybrids do not interact efficiently with proteins recognizing the NF-kappaB binding sites in genomic sequences. In addition, the data obtained indicate that the same NF-kappaB binding proteins recognize both the NF-kappaB DNA/PNA and DNA/DNA hybrids, but the molecular complexes generated with NF-kappaB DNA/PNA hybrids are less stable than those generated with NF-kappaB target DNA/DNA molecules.

Preferred conformation of peptides based on cycloaliphatic C(alpha,alpha)-disubstituted glycines: 1-amino-cycloundecane-1-carboxylic acid (Ac11c)

Two complete series of N-protected oligopeptide esters to the pentamer level from 1-amino-cycloundecane-1-carboxylic acid (Ac11c), an alpha-amino acid conformationally constrained through a medium-ring C(i)alpha<-->C(i)alpha cyclization, and either the L-Ala or Aib residue, along with the N-protected Ac11c monomer and homo-dimer alkylamides, have been synthesized by solution methods and fully characterized. The preferred conformation of these model peptides has been assessed in deuterochloroform solution by FT-IR absorption and 1H-NMR techniques. Furthermore, the molecular structures of one derivative (Z-Ac11c-OH) and two peptides (the tripeptide ester Z-Aib-Ac11c-Aib-OtBu and the pentapeptide ester Z-Ac11c-(Aib)2-Ac11c-Aib-OtBu) have been determined in the crystal state by X-ray diffraction. The experimental results support the view that beta-bends and 3(10)-helices are preferentially adopted by peptides rich in Ac11c, the second largest cycloaliphatic C(alpha,alpha)-disubstituted glycine known. This investigation has allowed the authors to approach the completion of a detailed conformational analysis of the whole 1-amino-cycloalkane-1-carboxylic acid (Ac(n)c, with n = 3-12) series, which represents the prerequisite for their recent proposal of the 'Ac(n)c scan' concept.

Bicyclic peptides as type I/type II beta-turn scaffolds

We recently reported the rational design, synthetics, and structural characterization of the most potent and selective peptide-based neurokinin A antagonist thus far described: cyclo(Met1-Asp2-Trp3-Phe4-Dap5-Leu6)cyclo(2 beta-5 beta). Its bicyclic structure is characterized by a type I and a type II two beta-turn around Trp3-Phe4 and Leu6-Met1, respectively. In order to understand whether the two different beta-turned structures are determined by the bicyclic structure or by the amino acid type at the corner positions, we have synthesized the pseudo-symmetrical analogue cyclo(Phe1-Asp2-Trp3-Phe4-Dap5-Trp6)cyclo(2 beta-5 beta). The structural characterization in the crystal state and in solution, here reported, gives an experimental evidence that the backbone of the bicyclic structure is a rigid scaffold that can be used to build both a type I and type II beta-turn independently from the amino acid composition.

Solution and solid state structure of an aib-containing cyclodecapeptide inhibiting the cholate uptake in hepatocytes

The conformational analysis of synthetic cyclodecapeptide c(Pro-Phe-phe-Aib-Leu)2 related to the cyclolinopeptide A, in the solid state and solution, has been carried out by x-ray diffraction and nmr spectroscopy. The structure of the monoclinic form obtained from methanol [a = 11.351 (5) A, b = 27.455 (2) A, c = 12.716 (8) A, beta = 99.65 (3) degrees; space group P2(1); Z = 2] shows the presence of six intramolecular NH...CO hydrogen bonds, with formation of four turns (three of type I and one of type III) and two C16 ring structures. All peptide units are trans. The solution structure, as found by nmr, indicates that, at room temperature, the peptide is conformationally homogeneous; the structure determined is perfectly symmetrical and topologically similar to that found in the solid state. The cyclodecapeptide exhibits similar biological activity to cyclolinopeptide A.

Bicyclic peptides as models of calcium binding sites: synthesis and conformation of a homodetic undecapeptide

A bicyclic undecapeptide of sequence cyclo-(Ala(1)-Pro(2)-Asp(3)-Glu(4)-Lys(5)-Ala(6)-Pro(7)-Asp(8)-Ser(9) -Glu(10))-cyclo-(10gamma --> 5varepsilon)-Gly(11), designed to mimic the calcium coordination site I of Calmodulin, has been synthesized and its conformation and calcium binding properties have been investigated by means of CD and nmr spectroscopy. The nmr analysis of the free peptide, carried out in DMSO and in TFE/H(2)O at different pH values, shows the presence in solution of one stable conformer, exhibiting trans configuration around both Proline residues. The nmr results in both solvents suggest for the molecule a rectangular shape constituted by two antiparallel beta-strands connected by two beta-turns. Interproton distances, evaluated by NOE contacts, have been used to obtain feasible models by means of Restrained Molecular Dynamic (RMD). The average models from RMD calculations, for both solvents, exhibit good analogies with Calmodulin site I. The model system, when compared with the reference system (Asp(20)-Glu(31) segment in CaM), shows similar dimensions and an effective superimposition of the respective sequence segments Ala(1)-Glu(4) and Thr(28)-Glu(31). The remaining segments of the model peptide exhibit a bending that is intermediate between that of the free and Ca(2+)-coordinated site I. CD spectra, recorded in TFE solutions, point to a 1:1 stoichiometry for the Ca(2+)-peptide complex, with an association constant of at least 1 x 10(5) M(-1).

[Surgical treatment of hemorrhoidal disease using circular mechanical stapler. Analysis of costs]

BACKGROUND

An analysis of surgical treatment costs of haemorrhoid disease with the use of a new circular stapler, is made comparing this operation with Milligan Morgan's technique. The money and management saving due to the reduction of operation time and postoperative stay compensates present costs due to stapler.

METHODS

35 uniform patients (number, age, sex, grade of haemorrhoid disease and surgical equipe) are considered and divided into two groups of study to evaluate perspectively the surgical costs.

RESULTS

The cost of treatment with stapler per patient is like Milligan Morgan's treatment (1.714.681 lire versus 1.681.893), with an important management saving of postoperative days (16 hours versus 42 hours).

CONCLUSIONS

Moreover there are psychologic and social advantages, not quantifiable but considerable, due to the early physical recovery and to the absence of out-patient dressing cycles peculiar of this surgical technique, with a rapid social and working reinstatement of patients (4-5 days versus 4-5 weeks of conventional intervention).

Solid state structural analysis of the cyclooctapeptide cyclo- (Pro1-Pro-Phe-Phe-Ac6c-Ile-D-Ala-Val8)

A solid state analysis of the cyclic octapeptide c(-Pro(1)-Pro-Phe-Phe-Ac(6)c-Ile-D-Ala-Val(8)-) (C8-CLA), containing the Pro-Pro-Phe-Phe sequence, followed by the bulky helicogenic C(alpha,alpha)-dialkylated 1-aminocyclohexane-1-carboxylic acid (Ac(6)c) residue and a D-Ala residue in position 7, has been carried out by x-ray diffraction. The crystals, grown from a DMSO solution, are monoclinic, space group P2(1) with a = 13.458(3) A, b = 19. 404(5) A, c = 21.508(4) A, and beta = 90.83(6) degrees, with two independent cyclic molecules in the asymmetric unit, two DMSO molecules, and three water molecules. The structure has been solved using the half and bake procedure by Sheldrick, and refined to final R1 and wR2 indices of 0.0613 and 0.1534 for 9867 reflections with I > 2sigma(I). This cyclic peptide, a deletion analogue of the naturally occurring cyclic nonapeptide cyclolinopeptide A [c(Pro-Pro-Phe-Phe-Leu-Ile-Ile-Leu-Val), CLA] has been designed to study the influence of the ring size reduction on the conformational behavior of CLA and more in general to obtain structural information on asymmetric cyclic octapeptides. The compound exhibits, in the solid state, a "banana-twisted" conformation with a cis peptide bond located between the two proline residues. Five intramolecular H bonds stabilize the structure: one type VIa beta-turn, two consecutive type III/I beta-turns, one gamma-turn, and one C(16) bend. The structure has also been compared with either the solution structure previously reported by us and obtained by nmr and computational analysis, and with solid state structural data reported in the literature on cyclic octapeptides.

Effect of lengthening of peptide backbone by insertion of chiral beta-homo amino acid residues: conformational behavior of linear peptides containing alternating L-leucine and beta-homo L-leucine residues

The synthesis and the solution behavior of the linear peptides containing a beta-homo (beta-H) leucine residue-Boc-Leu-beta-HLeu-Leu-OMe, Boc-beta-HLeu-Leu-beta-HLeu-Leu-OMe, and Boc-Leu-beta-HLeu-Leu-beta-HLeu-Leu-OMe-as well as the solid structure of the tripeptide, are reported. The conformational behavior of the peptides was investigated in solution by two-dimensional nmr. Our data support the existence in solution with different families of conformers in rapid interchange. The crystals of the tripeptide are orthorhombic, space group P2(1)2(1)2, with a = 15.829(1) A, b = 29.659(1) A, c = 6.563(1) A, and Z = 4. The structure has been solved by direct methods and refined to final R1 and wR2 indexes of 0.0530 and 0.1436 for 2420 reflections with I > 2sigma(I). In the solid state, the tripeptide does not present intramolecular H bonds, and the peptide backbone of the two leucine residues adopts a quasi-extended conformation. For the beta-HLeu residue, the backbone conformation is specified by the torsion angles straight phi(2) = -120.9(4) degrees, mu(2) = 56.7(4) degrees, psi(3) = -133.2(4) degrees. The side chains of the three residues assume the same conformation (g(-), g(-), trans), and all peptide bonds, except the urethane group at the N-terminus, are in the trans conformation. Preliminary conformational energy calculations carried out on the Ac-NH-beta-HAla-NHMe underline that the conformations with mu angle equal to 180 degrees and 60 degrees assume lower energy with respect to the others. In addition, we found a larger conformational freedom for the psi angle with respect to the straight phi angle.

Conformational behavior of C alpha,alpha-diphenyl glycine: extended conformation in tripeptides containing consecutive D phi G residues

Recent studies on the conformational preferences of the Dphig (C(alpha,alpha)-diphenylglycine) residue showed that this C(alpha,alpha)-disubstituted glycine has a structural versatility. In fact, depending on the nature of the following or preceding residue, Dphig can assume either folded or extended conformations. We have carried out the analysis of the conformational preferences of the Dphig residue in tripeptides containing consecutive Dphig residues. The crystal structures of Z-Dphig-Dphig -Dphig-OMe (a; Z = benzyloxycarbonyl; OMe = methyl ester), Z-Aib-Dphig-Dphig-OMe (b; Aib = alpha-aminoisobutyric acid), and Z-Ac(3)c-Dphig-Dphig-OMe (c; Ac(3)c = alpha-amino-cyclopropan carboxylic acid), are here reported. The Dphig residues adopt the fully extended conformation in the three tripeptides examined. Together with our previous findings on Dphig containing peptides, the structures of the peptides here examined, indicate that the presence of adjacent Dphig residue in the sequence further stabilizes the extended conformation.