Management of Inflammatory Aortic Aneurysms - A Scoping Review.

OBJECTIVE: Inflammatory abdominal aortic aneurysms (InflAAAs) account for 5 - 10% of aortic aneurysms and are characterised by retroperitoneal fibrosis. Diagnosis is often delayed, and doubts remain about the optimal management strategy. This scoping review describes the current state of knowledge on InflAAAs. METHODS: Medline, PubMed, EMBASE, and Scopus were searched for relevant studies that evaluated the diagnosis and treatment of InflAAAs. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol was followed. RESULTS: Fifty-seven papers were selected (low level of evidence), which included 1 554 patients, who were mostly male and heavy smokers. A triad of chronic abdominal or back pain, weight loss, and elevated inflammatory markers was highly suggestive of the diagnosis but rarely present, and fever was noted only randomly. A mantle sign was seen on computed tomography angiography (CTA) in 73 - 100% of patients. Open surgical repair (OSR) and endovascular aortic aneurysm repair (EVAR) was reported in 1 376 and 178 patients, respectively. OSR was associated with significant iatrogenic bowel (n = 22), urinary tract system (n = 7), venous (n = 30), pancreatic (n = 6), and splenic (n = 5) injuries, while EVAR was associated with lower 30 day mortality (0 - 5% vs. 0 - 32%). One and two year mortality rates were similar between the two treatment modalities (0 - 20% and 0 - 36%, respectively). EVAR was more often associated with post-operative progression of inflammation (17% vs. 0.4%), and a higher frequency of persistent hydronephrosis (> 50%) and limb occlusion (20%). Used in < 10% of patients, corticosteroids led to complete pain relief and a reduction in peri-aortic inflammation within 6 - 18 months. CONCLUSION: InflAAAs are characterised by non-specific symptoms, with the mantle sign on CTA being pathognomonic. Corticosteroids may be considered a basic treatment that all patients should receive initially. Low quality data indicate that EVAR (vs. OSR) is associated with fewer intra-operative complications and lower peri-operative mortality but more late fibrosis related adverse events. International multicentre registries are required to gather more insights into this challenging pathology.

Selective crossectomy combined with mechanochemical ablation in the treatment of great saphenous vein insufficiency: Early results of a single center experience.

BACKGROUND: Selective crossectomy and mechanochemical ablation (MOCA) of great saphenous vein (GSV) have been used, for years, individually in the treatment of chronic venous insufficiency. In this paper, we focus on the advantages of a combination of the two techniques, in order to prevent complications and recurrence. METHODS: A preoperative clinical and instrumental screening phase was conducted for the purpose of dividing patients into three groups: "Saph+Cross" group (51/139 patients) underwent saphenectomy and crossectomy; "MOCA" group (44/139 patients) underwent MOCA of GSV with Flebogrif® device; "MOCA + Cross" group (44/139 patients) subjected to both MOCA and crossectomy procedures.Recurrence rate, defined as total recanalization of GSV and/or onset of neosaphena and/or new varicose veins, was used as a primary outcome. Secondary outcomes were procedural time and intra- and post-procedural complications. RESULTS: We conducted a 1-, 6-, and 12-month follow-up with Duplex scan. The recurrence rates were 3.9%, 21.8%, and 4.5% for "Saph+Cross," "MOCA," and "MOCA+Cross," respectively, with a significant difference for the comparison between "MOCA" and "Saph+Cross" (MOCA vs Saph+Cross: OR 5.35, CI95% [0.98; 54.6], p-value .040).The sub-analysis of primary outcome highlighted a lower recanalization rate of GSV when combining the crossectomy with MOCA procedure (2.2% MOCA+Cross vs 15.9% MOCA; 0.12 OR, [0.002; 1.02] CI95%, p-value .029).Among the secondary outcomes, "MOCA" showed a shorter procedural time than the other groups (Saph+Cross: 51.3 ± 11.4; MOCA: 45.1 ± 7.5; MOCA+Cross: 50.4 ± 10; p-value .027). No significant differences were noted in terms of intra- and post-procedural complications. CONCLUSIONS: The results showed that patients treated with saphenectomy and crossectomy have a lower recurrence rate compared to MOCA alone and MOCA + crossectomy procedures.The association of crossectomy with MOCA significantly reduces the recanalization rate of GSV, and it is also characterized by a higher free survival from recurrence (SSF) than with MOCA alone.

Ternary copper(II) complexes with 1,10­phenanthroline and various aminoacidates: A spectroscopic and voltammetric study in aqueous solution.

Ternary copper(II) complexes with 1,10­phenanthroline and the aminoacids l­arginine, l­aspartic acid, l­histidine, l­glutamic acid, l­glutamine, l­leucine, l­lysine, l­methionine, l­phenylalanine, l­tryptophan, l­tyrosine, l­valine, were studied in aqueous solution by means of UV-Vis-NIR spectrophotometry, EPR spectroscopy either at room or at low temperatures, and Square Wave Voltammetry. From the experimental data it is possible to conclude that most of these ternary complexes show a pseudo-octahedral geometry with a CuN3O in plane chromophore and two oxygen atoms coming from water molecules perpendicularly bound to the equatorial plane. An exception to this general behaviour is given by the ternary copper(II) complex with 1,10­phenanthroline and histidine at pH value near the neutrality because of the terdentate nature of histidine when it coordinates by means of its histamine-like mode. In this case, evidence for a probable square-based pyramidal stereochemistry is given in support. At pH values around 5 the histidine behaves as bidentate ligand coordinating by its glycine-like mode, so as the copper(II) ternary complex with 1,10­phenathroline shows the pseudo-octahedral geometry found for all the ternary complexes with the other aminoacids. Moreover the ternary complex species with histidine at pH 5 and 7 are in equilibrium with each other as a function of the aqueous solution pH value and the temperature. In fact, the examination of low temperature EPR spectra at pH near 7 revealed not only a square-based pyramid complex but also products of decomposition. These results were also confirmed by the trend found in the formal redox potentials by the voltammetric measurements on many of these ternary complexes.

Pancreas Transplantation at a Single Latin-American Center; Overall Results with Type 1 and Type 2 Diabetes Mellitus.

BACKGROUND: Simultaneous pancreas-kidney transplantation (SPK) has become the treatment of choice for type 1 diabetes mellitus (T1DM) patients with chronic renal failure. Type 2 diabetes mellitus (T2DM), was once considered to be a contraindication for pancreas transplantation; however, it has been accepted as a new indication, under strict criteria. Although favorable results have increase the indication for T2DM in developed countries, there have been no reports of long-term results for this indication from Latin American centers. METHODS: From April 2008 to March 2016, patients receiving SPK or pancreas transplant alone (PTA) for T2DM were included and compared with T1DM recipients. Variables were compared between groups with the use of χ2 and t tests; Kaplan-Meier with log rank was used for patient and graft survivals; P < .05 was considered to be significant. RESULTS: A total of 45 SPK and 1 PTA were performed, 35 (76.1%) for T1DM and 11 (24.5%) for T2DM. Mean pre-transplantation C-peptide was significantly higher in the T2DM group (P = .01); HbA1c was higher in the T1DM group (P = .03). No differences were found in weight, body mass index, and pre-transplantation glycemia. Patient survivals for T1DM recipients were 88.2% and 84.8% at 1 and 5 years, respetively, versus 100% and 74.1% for T2DM recipients (P = .87). CONCLUSIONS: Our initial prospective experience in a single Latin American center showed that medium- and long-term outcomes for T1DM and T2DM individuals receiving pancreas transplants are similar, under strict selection criteria.

Simple and mixed complexes of copper(II) with 8-hydroxyquinoline derivatives and amino acids: Characterization in solution and potential biological implications.

Copper(II) complexes with 8-hydroxyquinoline (8-HQ) and two 8-HQ derivatives, namely clioquinol (CQ) and 5,7-dichloro-2-[(dimethylamino)methyl]quinolin-8-ol (PBT2), were investigated in organic and, where feasible, in aqueous solutions. This class of compounds is of particular interest in neurological disorders since they may act as metal-protein attenuating compounds and may help redistributing metal ions and restoring intracellular metal reserves, which are often perturbed in neurological patients. Several techniques, like potentiometry, UV-Vis absorption, electron paramagnetic resonance (EPR), cyclic voltammetry and electrospray ionisation-mass spectrometry (ESI-MS), were used to obtain information on both the formation of copper(II) complexes in solution as well as on the structure of their species. Multi-wavelength treatment of UV-Vis data clearly indicated the formation of both [Cu(PBT2)]+ and [Cu(PBT2)2] species; the speciation was also supported by ESI-MS data. The EPR results showed that the mono- and bis-copper(II) complexes with PBT2 have square-based pyramidal structures while the bis-copper (II) complexes with CQ or 8-HQ have square-planar o pseudo-octahedral geometries. The formation of copper(II) ternary complexes with 8-HQ, CQ and PBT2 and some selected neurotransmitters (glycine, glutamate and histidine) is also reported. Except for the copper(II) ternary complex with PBT2 and His, almost all ternary complexes have molecular geometries, which are not different from those of the bis-complexes. Interestingly the ternary copper(II) complexes, containing CQ, 8-HQ and PBT2 and glycine, glutamate or histidine turned out to be more soluble in aqueous solution than their binary complexes with parent 8-HQ derivatives; the copper(II) complexes can also be reduced more easily than their parent bis-complexes.

Copper ion interaction with the RNase catalytic site fragment of the angiogenin protein: an experimental and theoretical investigation.

The angiogenin protein (Ang) is a member of the vertebrate-specific secreted ribonucleases and one of the most potent angiogenic factors known. Ang is a normal constituent of human plasma and its concentration increases under some physiological and pathological conditions to promote neovascularization. Ang was originally identified as an angiogenic tumour factor, but its biological activity has been found to extend from inducing angiogenesis to promoting cell survival in different neurodegenerative diseases. Ang exhibits weak ribonucleolytic activity, which is critical for its biological functions. The RNase catalytic sites are two histidine residues, His-13 and His-114, and the lysine Lys-40. Copper is also an essential cofactor in angiogenesis and influences angiogenin's biological properties. The main Cu(ii) anchoring site of Ang is His-114, where metal binding inhibits RNase activity of the protein. To reveal the Cu(ii) coordination environment in the C-terminal domain of the Ang protein, we report on the characterization, by means of potentiometric, voltammetric, and spectroscopic (CD, UV-Vis and EPR) methods and DFT calculations, of Cu(ii) complexes formed with a peptide fragment including the Ang sequence 112-117 (PVHLDQ). Potentiometric titrations indicated that [CuLH-2] is the predominant species at physiological pH. EPR, voltammetric data and DFT calculations are consistent with a CuN3O2 coordination mode in which a distorted square pyramidal arrangement of the peptide was observed with the equatorial positions occupied by the nitrogen atoms of the deprotonated amides of the Asp and Leu residues, the δ-N atom of histidine and the oxygen atom of the aspartic carboxylic group. Moreover, two analogous peptides encompassing the PVHLNQ and LVHLDQ sequences were also characterized by using thermodynamic, spectroscopic and DFT studies to reveal the role they play in Cu(ii) complex formation by the carboxylate side chain of the Asp and Pro residues, a known breaking-point in metal coordination.

Surveillance Registry of Sirolimus Use in Recipients of Kidney Allografts From Expanded Criteria Donors.

BACKGROUND: The use of expanded criteria donor (ECD) kidneys has increased the overall availability of renal transplants. This study assessed the use of sirolimus in patients receiving Argentina-ECD kidneys. METHODS: This observational, open-label, 1-arm, prospective, longitudinal pilot study was conducted at 8 transplant centers in Argentina. Adults receiving kidney transplants (without pancreas) from ECDs were eligible if they were converted to sirolimus 1 to 36 months' posttransplantation, with sirolimus becoming base therapy within 1 month after conversion. Patients were followed up for 1 year. Outcomes included reasons for conversion, acute rejection, patient and graft survival, graft status, and safety. RESULTS: The intention-to-treat population included 52 patients (mean age, 48.7 years). Calcineurin inhibitor nephropathy (40%) and chronic allograft nephropathy (25%) were the most frequent reasons for conversion. Two acute rejections occurred during follow-up, but no patients experienced graft loss. One patient died during follow-up, and 3 patients died within 1 month of the last sirolimus dose. Levels of serum creatinine and creatinine clearance remained stable from baseline to week 52/53. Mean proteinuria measured in a subset of patients was 0.2 ± 0.2 g/24 hours before conversion and increased to 0.6 ± 1.2 g/24 hours at week 24/25 and 0.5 ± 0.6 g/24 hours at week 52/53. Adverse events were consistent with those in previous conversion trials; the most common were infections and infestations (54%). CONCLUSIONS: This pilot study illustrates the potential benefits of sirolimus in recipients of ECD kidneys in Argentina. Larger, randomized controlled trials are needed to confirm these findings and to clarify the long-term benefits of sirolimus in this patient population.

Solution equilibria and the X-ray structure of Cu(ii) complexation with 3-amino-N-(pyridin-2-ylmethyl)propanamide, a pseudo-mimic of human serum albumin.

Copper complexes have anti-inflammatory activity in the treatment of inflammation associated with rheumatoid arthritis (RA). The preferred route of administration is through the skin, so the rate of dermal absorption and bioavailability of copper is important. Based on previous studies, 3-amino-N-(pyridin-2-ylmethyl)-propanamide, [H(56)NH2], was designed as a potential chelator of copper. The stability constant measurements revealed that MLH-1 is the most stable species at the physiological pH of 7.4. The X-ray crystal structure of this species was solved and copper was found in a rectangular pyramidal geometry. The ligand occupied three coordination sites while bridging chloride linked copper ions together in a chain. The ligand bound to the metal ion through the pyridyl nitrogen, the amide nitrogen and the terminal amino group. Spectroscopic studies confirmed that this structure persisted in aqueous solution. Octanol/water partition coefficients and Franz cell permeation studies showed that [H(56)NH2] is able to promote the dermal absorption of Cu(ii).

Thrombosis of abdominal aorta in congenital afibrinogenemia: case report and review of literature.

Thrombotic events in congenital hypo-afibrinogenemia have been rarely reported, either in association or not with replacement therapy or thrombotic risk factors. We describe clinical findings and management of thrombosis of abdominal aorta with peripheral embolism in a patient with congenital afibrinogenemia. A review of arterial thrombosis in inherited hypo-afibrinogenemia was also performed. The patient with a severe bleeding history requiring prophylaxis with fibrinogen concentrates (FC) was admitted for ischaemia of the 4th right toe. An angio-CT of abdominal aorta showed a thrombosis from the origin of renal arteries to the carrefour with a distal floating part. No thrombotic risk factors were found; a previous traumatic lesion of aortic wall might have triggered the thrombus formation, whereas the role of FC prophylaxis remains uncertain. The patient was successfully treated with FC, enoxaparin followed by fondaparinux, and low-dose aspirin without bleeding or thrombosis recurrence. After 2 years, aortic thrombus was almost completely recovered. Sixteen hypo/afibrinogenemia patients with arterial thrombosis were found in Literature, showing that thrombosis often occurs at a young age, involves large vessels, its recurrence is not unusual, and therapeutic strategy is not defined yet. Our therapeutic approach was effective and also safe, but further studies are needed to improve the knowledge of pathogenesis and the anti-thrombotic management in this peculiar setting.

First epidemiologic study in Argentina of the prevalence of BK viruria in kidney transplant patients.

BACKGROUND: The worldwide seroprevalence of human BK polyomavirus (BKV) in adults is 80%. About 10%-60% of renal transplant recipients experience BKV infection, nephropathy of the graft may occur in 5% of the cases, and up to 45% lose the graft. The aim of this work was to describe the prevalence of BK viruria during the 1st year after transplantation. METHODS: An epidemiologic multicenter cross-sectional study was carried out in consecutive patients at each site with kidney transplantation from August 2011 to July 2012. Clinically significant viruria was defined as >10(7) copies/mL. Viral DNA was extracted with the use of silica columns. Quantification was performed with the use of real-time polymerase chain reaction with primers that amplify a fragment of the large T-antigen gene and with a specific Taqman-MGB probe for BKV. For each assay, a standard curve with a quantified plasmid was included. RESULTS: Of 402 renal transplant recipients at 18 renal transplant sites, we analyzed 382; median age was 46.33 years, and 46.40% were female. The median of the temporal distribution for urine samples was 153 days. BK virus was detected in 50/382 samples (13%), 18 with values >10(7) copies/mL (4.7%). The median of the distribution of positive values was 123 days and the highest frequency of positive values was in months 3-7. The conditions of recipient older than 34 years and donor older than 41 years were the only ones that showed statistically significant association with BK viruria. No association with any specific immunosuppressive drug was observed. CONCLUSIONS: This is the first multicenter study conducted in Argentina to determine the prevalence of BK viruria in renal transplant recipients. Because of the growing number of the population susceptible to this infection, it is important to register and describe data about its epidemiology and associated risk factors.

Short- and long-term outcomes of every graft recovered during a multi-organ procurement procedure including the intestine.

BACKGROUND: The development of intestinal transplant (Tx) programs introduces thymoglobulin donor treatment as well as an almost complete warm dissection of the abdominal organs to allocate them to different recipients. Our aim is to assess the reproducibility and feasibility of the surgical technique of multi-organ procurement with the use of thymoglobulin donor pre-treatment and report the short- and long-term outcomes of every graft harvested as part of multi-organ procurement (MTOp), including the intestine. METHODS: Data were collected of all organs harvested from MTOp, including the intestines allocated to our center from March 2006 to July 2011. Data from 92 recipients and 116 organs procured from 29 MTOp were analyzed. Twelve hearts, 2 lungs, and 1 cardio-pulmonary block were transplanted; primary graft dysfunction developed in 4 of the 12 hearts and in the cardio-pulmonary block. RESULTS: The survival rate was 75% and 100% for hearts and lungs, respectively. Nineteen livers, 9 kidney-pancreas, 19 kidneys, and 29 intestines were transplanted. Delayed graft function (DGF) of the pancreas developed in 3 of 9 kidney-pancreas, and the other 3 exhibited DGF of the kidney; 4 of 19 Tx kidneys had DGF. The survival was 84%, 78%, 95%, and 65.5% for livers, kidney-pancreas, kidneys, and intestines, respectively. CONCLUSIONS: Organs procured during MTOp including the intestine can be safely used, increasing organ availability and transplant applicability without compromising allocation, quality, and long-term results of the non-intestinal-procured organs.

Determination of formal redox potentials in aqueous solution of copper(II) complexes with ligands having nitrogen and oxygen donor atoms and comparison with their EPR and UV-Vis spectral features.

Formal redox potentials in aqueous solution were determined for copper(II) complexes with ligands having oxygen and nitrogen as donor atoms. All the chosen copper(II) complexes have well-known stereochemistries (pseudo-octahedral, square planar, square-based pyramidal, trigonal bipyramidal or tetrahedral) as witnessed by their reported spectroscopic, EPR and UV-visible (UV-Vis) features, so that a rough correlation between the measured redox potential and the typical geometrical arrangement of the copper(II) complex could be established. Negative values have been obtained for copper(II) complexes in tetragonally elongated pseudo-octahedral geometries, when measured against Ag/AgCl reference electrode. Copper(II) complexes in tetrahedral environments (or flattened tetrahedral geometries) show positive redox potential values. There is a region, always in the field of negative redox potentials which groups the copper(II) complexes exhibiting square-based pyramidal arrangements. Therefore, it is suggested that a measurement of the formal redox potential could be of great help, when some ambiguities might appear in the interpretation of spectroscopic (EPR and UV-Vis) data. Unfortunately, when the comparison is made between copper(II) complexes in square-based pyramidal geometries and those in square planar environments (or a pseudo-octahedral) a little perturbed by an equatorial tetrahedral distortion, their redox potentials could fall in the same intermediate region. In this case spectroscopic data have to be handled with great care in order to have an answer about a copper complex geometrical characteristics.

Electrochemical characterization of ordered arrays of metallo-porphyrins in aqueous solution.

Metallated meso-tetrakis(N-methyl-4-pyridyl)porphyrin (MTMPyP) and 5,11,17,23-tetrasulfonato-25,26,27,28-tetrakis-(hydroxylcarbonylmethoxy)-calix[4]arene (C(4)TsTc) were used as key components for building up discrete supramolecular entities starting from the formation of the template species MTMPyP:C(4)TsTc (1 : 4, M = Cu, Zn). The stepwise addition of further amount of porphyrin allows the facile non-covalent synthesis of discrete supramolecular entities (2 : 4 and 3 : 4) which can be built up just by programming the right stoichiometric addition of the proper porphyrin. The redox potentials of these supramolecular complexes in aqueous media, as well as those of the parent metalloporphyrins, have been characterized by using square wave voltammetry technique. The use of the simulation procedure leads us to establish the electrochemical steps involved in the redox processes for each supramolecular species, evidencing multistep electron reductions which were not experimentally resolved clearly because of their closeness. The most striking result is that the electrochemistry of each of these supramolecular complexes is different from that of the parent components. This "anomalous" behavior can be explained only considering each of these supramolecular complexes as a unique entity, in which such an internal electronic communication might occur. The formation of the 1 : 4 supramolecular complex produces a negative shift as to the metallated porphyrin redox potentials of about 30 mV. In the case of 2 : 4 and 3 : 4 species, the redox potentials progressively shifts towards more positive values by about 10-15 mV for each complexation step.

Copper complex species within a fragment of the N-terminal repeat region in opossum PrP protein.

A spectroscopic (UV-Vis, CD and EPR), thermodynamic and voltammetric study of the copper(ii) complexes with the Ac-PHPGGSNWGQ-NH(2) polypeptide (L), a fragment of the opossum PrP protein N-terminal four-repeat region, was carried out in aqueous solution. It suggests the formation of a highly distorted [Cu(L)H(-2)] complex species in the neutral region, the stereochemistry of which is ascribable to a square base pyramid and a CuN(3)O(2) chromophore, resulting from the coordination of a histidine imidazole and two peptide nitrogen atoms and probably oxygen atoms from water molecules. At basic pH values a [Cu(L)H(-3)](-) species with a pseudo-octahedral geometry was also obtained, with four nitrogen donor atoms in its equatorial plane, coming from the histidine residue and from peptidic nitrogen atoms. Interestingly, at pH values relatively higher than the neutrality, the coordination sphere of the copper complex in the [Cu(L)H(-2)] species changes its stereochemistry towards a pseudo-octahedron, as suggested by the change in the parallel copper hyperfine coupling constant of the EPR spectra at low temperature. A slight difference in the redox potentials between this two-faced [Cu(L)H(-2)] complex species seems to confirm this behaviour. Both potentiometric and spectroscopic data were compared with the analogous species obtained with the Ac-PHGGGWGQ-NH(2) peptide, belonging to the octarepeat domain of the human prion protein (hPrP) N-terminal region. The [Cu(L)H(-2)] species formed by the Ac-PHPGGSNWGQ-NH(2) decapeptide, having a slightly lower stability, turned out to be less abundant and to exist within a narrow pH range.

Individualizing early use of sirolimus in renal transplantation.

One of the main goals in the current care of kidney transplant recipients is to extend long-term graft survival. Efficacious immunosuppressive agents devoid of nephrotoxicity are needed. In human clinical transplantation, sirolimus combined with other immunosuppressive drugs has proven to be a powerful immunosuppressant capable of preventing acute graft rejection, as well as of improving renal function, renal histology, and graft survival when compared with immunosuppressive regimens that include calcineurin inhibitors. The valuable experience gained through many clinical studies allows clinicians to plan sirolimus use. We present a review of the clinical experience and literature review on the use of sirolimus in the first 12 months posttransplantation.

Copper(II) complex formation with a linear peptide encompassing the putative cell binding site of angiogenin.

Angiogenin is one of the more potent angiogenic factors known, whose activity may be affected by the presence of copper ions. Copper(II) complexes with the peptides encompassing the putative endothelial cell binding domain of angiogenin, Ac-KNGNPHREN-NH(2) and Ac-PHREN-NH(2), have been characterized by potentiometric, UV-vis, CD and EPR spectroscopic methods. The coordination features of all the copper complex species derived by both peptides are practically the same, as predictable because of the presence of a proline residue within their aminoacidic sequence. In particular, Ac-PHREN-NH(2) is really the aminoacidic sequence involved in the binding to copper(II). Thermodynamic and spectroscopic evidence are given that side chain oxygen donor atom of glutamyl residue is involved in the copper binding up to physiological pH. EPR parameters suggest that the carboxylate group is still involved also in the predominant species [Cu(L)H(-2)], the metal coordination environment being probably formed by N(Im), 2N(-), H(2)O in equatorial plane and an oxygen atom from COO(-) in apical position, or vice versa, with the carboxylate oxygen atom in the copper coordination plane and the water molecule confined to one of the apical positions. Moreover, the comparison with the thermodynamic and spectroscopic results in the case of the copper(ii) complex species formed by the single point mutated peptide, Ac-PHRQN-NH(2), provides further evidence of the presence of carboxylate oxygen atom in the copper coordination sphere.

A doppel alpha-helix peptide fragment mimics the copper(II) interactions with the whole protein.

The doppel protein (Dpl) is the first homologue of the prion protein (PrP(C)) to be discovered; it is overexpressed in transgenic mice that lack the prion gene, resulting in neurotoxicity. The whole prion protein is able to inhibit Dpl neurotoxicity, and its N-terminal domain is the determinant part of the protein function. This region represents the main copper(II) binding site of PrP(C). Dpl is able to bind at least one copper ion, and the specific metal-binding site has been identified as the histidine residue at the beginning of the third helical region. However, a reliable characterization of copper(II) coordination features has not been reported. In a previous paper, we studied the copper(II) interaction with a peptide that encompasses only the loop region potentially involved in metal binding. Nevertheless, we did not find a complete match between the EPR spectroscopic parameters of the copper(II) complexes formed with the synthesized peptide and those reported for the copper(II) binding sites of the whole protein. Herein, the synthesis of the human Dpl peptide fragment hDpl(122-139) (Ac-KPDNKLHQQVLWRLVQEL-NH(2)) and its copper(II) complex species are reported. This peptide encompasses the third alpha helix and part of the loop linking the second and the third helix of human doppel protein. The single-point-mutated peptide, hDpl(122-139)D124N, in which aspartate 124 replaces an asparagine residue, was also synthesized. This peptide was used to highlight the role of the carboxylate group on both the conformation preference of the Dpl fragment and its copper(II) coordination features. NMR spectroscopic measurements show that the hDpl(122-139) peptide fragment is in the prevailing alpha-helix conformation. It is localized within the 127-137 amino acid residue region that represents a reliable conformational mimic of the related protein domain. A comparison with the single-point-mutated hDpl(122-139)D124N reveals the significant role played by the aspartic residue in addressing the peptide conformation towards a helical structure. It is further confirmed by CD measurements. Potentiometric titrations were carried out in aqueous solutions to obtain the stability constant values of the species formed by copper(II) with the hDpl peptides. Spectroscopic studies (EPR, NMR, CD, UV/Vis) were performed to characterize the coordination environments of the different metal complexes. The EPR parameters of the copper(II) complexes with hDpl(122-139) match those of the previously reported copper(II) binding sites of the whole hDpl. Addition of the copper(II) ion to the peptide fragment does not alter the helical conformation of hDpl(122-139), as shown by CD spectra in the far-UV region. The aspartate-driven preorganized secondary structure is not significantly modified by the involvement of Asp124 in the copper(II) complex species that form in the physiological pH range. To elaborate on the potential role of copper(II) in the recently reported interaction between the PrP(C) and Dpl, the affinity of the copper(II) complexes towards the prion N terminus domain and the binding site of Dpl was reported.

Copper(II) complexes of prion protein PEG11-tetraoctarepeat fragment: spectroscopic and voltammetric studies.

Spectroscopic (UV-Vis and EPR) and voltammetric studies have been carried out on the copper(II) complexes with the Ac-PEG11-(PHGGGWGQ)4-NH2 (L) polypeptide. In the ratios Cu : L 3 : 1 and 4 : 1, the two [Cu3(L)H(-6)] and [Cu4(L)H(-8)] complex species have been characterized at neutral pH values. All the copper atoms occupy similar coordination sites formed by imidazole, peptidic nitrogen atoms and carbonyl oxygen atoms in a square base pyramidal geometry. Voltammetric measurements on these systems point out the cooperativity in the electron transfer processes among the copper(II) sites during their reduction. NO interaction with these polynuclear copper species is characterized by the reduction of the copper sites through the formation of two different intermediate complex species. When an excess of the Ac-PEG11-(PHGGGWGQ)4-NH2 ligand is considered, frozen solution EPR parameters and UV-Vis spectroscopic data identify the [Cu(N(im))4]2+ chromophore, which does not interact with NO.

Copper(II) complexes with peptide fragments encompassing the sequence 122-130 of human doppel protein.

Copper(II) complexes of the peptide fragment (Dpl122-130) encompassing the sequence 122-130 of human doppel protein were characterized by potentiometric, UV-Visible, CD and EPR spectroscopic methods. An analogous peptide, in which the aspartate residue was substituted by an asparagine amino acid, was synthesized in order to provide evidence on the possible role of carboxylate group in copper(II) coordination. It was found that the carboxylic group is directly involved in copper(II) coordination at acidic pH, forming the CuLH(2) species with Dpl122-130. This copper(II) complex displayed EPR parameters very similar to those of the analogous complex with the whole doppel protein. At pH higher than 7, the complexes showed magnetic parameters similar to those of the major species of protein formed in the pH range 7-8, with the metal coordination environment consisting of one imidazole and three amide nitrogen atoms. The comparison of Cu-Dpl122-130 binding constant values with those of the prion peptide fragments (PrP106-114), showed that doppel peptide had a higher metal binding affinity at acidic pH whereas the prion peptide fragment binds the metal tightly at physiological pH.

Copper(II) complexes with an avian prion N-terminal region and their potential SOD-like activity.

Potentiometric and spectroscopic (UV-Vis, CD and EPR) studies were carried out on copper(II) complexes with chicken prion protein N-terminal fragments, Ac-(PHNPGY)(4)-NH(2), and the mutated residue, Ac-(PHNPGF)(4)-NH(2), to assess the role of tyrosine in the copper coordination. Both thermodynamic and spectroscopic results indicate that chicken prion fragments are not able to bind more than two copper ions and only with the involvement of side chain tyrosine groups. The prevailing complex shows one copper ion bound to four imidazole nitrogen atoms in the 1:1 metal to ligand ratio systems. The superoxide dismutase (SOD)-like activity of copper(II) complexes with the avian peptides and mammal analogue, Ac-(PHGGGWGQ)(4)-NH(2), was also investigated by means of Pulse radiolysis. The copper(II) complexes with avian peptides do not display SOD-like activity, while very low activity has been detected for the copper(II) complexes with mammalian tetraoctarepeat.