Designing Fluorescent Nuclear Permeable Peptidomimetics to Target Proliferating Cell Nuclear Antigen

Human proliferating cell nuclear antigen (PCNA) is a critical mediator of DNA replication and repair, acting as a docking platform for replication proteins. Disrupting these interactions with a peptidomimetic agent presents as a promising avenue to limit proliferation of cancerous cells. Here, a p21-derived peptide was employed as a starting scaffold to design a modular peptidomimetic that interacts with PCNA and is cellular and nuclear permeable. Ultimately, a peptidomimetic was produced which met these criteria, consisting of a fluorescein tag and SV40 nuclear localization signal conjugated to the N-terminus of a p21 macrocycle derivative. Attachment of the fluorescein tag was found to directly affect cellular uptake of the peptidomimetic, with fluorescein being requisite for nuclear permeability. This work provides an important step forward in the development of PCNA targeting peptidomimetics for use as anti-cancer agents or as cancer diagnostics.

PPARγ Corepression Involves Alternate Ligand Conformation and Inflation of H12 Ensembles

Inverse agonists of peroxisome proliferator activated receptor γ (PPARγ) have emerged as safer alternatives to full agonists for their reduced side effects while still maintaining impressive insulin-sensitizing properties. To shed light on their molecular mechanism, we characterized the interaction of the PPARγ ligand binding domain with SR10221. X-ray crystallography revealed a novel binding mode of SR10221 in the presence of a transcriptionally repressing corepressor peptide, resulting in much greater destabilization of the activation helix, H12, than without corepressor peptide. Electron paramagnetic resonance provided in-solution complementary protein dynamic data, which revealed that for SR10221-bound PPARγ, H12 adopts a plethora of conformations in the presence of corepressor peptide. Together, this provides the first direct evidence for corepressor-driven ligand conformation for PPARγ and will allow the development of safer and more effective insulin sensitizers suitable for clinical use.

Hippo signaling instructs ectopic but not normal organ growth

The Hippo signaling pathway is widely considered a master regulator of organ growth because of the prominent overgrowth phenotypes caused by experimental manipulation of its activity. Contrary to this model, we show here that removing Hippo transcriptional output did not impair the ability of the mouse liver and Drosophila eyes to grow to their normal size. Moreover, the transcriptional activity of the Hippo pathway effectors Yap/Taz/Yki did not correlate with cell proliferation, and hyperactivation of these effectors induced gene expression programs that did not recapitulate normal development. Concordantly, a functional screen in Drosophila identified several Hippo pathway target genes that were required for ectopic overgrowth but not normal growth. Thus, Hippo signaling does not instruct normal growth, and the Hippo-induced overgrowth phenotypes are caused by the activation of abnormal genetic programs.

Unlocking the PIP-box: A peptide library reveals interactions that drive high-affinity binding to human PCNA

The human sliding clamp, Proliferating Cell Nuclear Antigen (hPCNA), interacts with over 200 proteins through a conserved binding motif, the PIP-box, to orchestrate DNA replication and repair. It is not clear how changes to the features of a PIP-box modulate protein binding and thus how they fine-tune downstream processes. Here, we present a systematic study of each position within the PIP-box to reveal how hPCNA-interacting peptides bind with drastically varied affinities. We synthesized a series of 27 peptides derived from the native protein p21 with small PIP-box modifications and another series of 19 peptides containing PIP-box binding motifs from other proteins. The hPCNA-binding affinity of all peptides, characterized as K_D values determined by surface plasmon resonance, spanned a 4000-fold range, from 1.83 nM to 7.59 μM. The hPCNA-bound peptide structures determined by X-ray crystallography and modeled computationally revealed intermolecular and intramolecular interaction networks that correlate with high hPCNA affinity. These data informed rational design of three new PIP-box sequences, testing of which revealed the highest affinity hPCNA-binding partner to date, with a K_D value of 1.12 nM, from a peptide with PIP-box QTRITEYF. This work showcases the sequence-specific nuances within the PIP-box that are responsible for high-affinity hPCNA binding, which underpins our understanding of how nature tunes hPCNA affinity to regulate DNA replication and repair processes. In addition, these insights will be useful to future design of hPCNA inhibitors.

Ultra-low fouling photocrosslinked coatings for the selective capture of cells expressing CD44

The effective control of biointerfacial interactions is of outstanding interest in a broad range of biomedical applications, ranging from cell culture tools to biosensors and implantable medical devices. For many of these applications, highly specific interactions between cells and material surfaces are desired. Sophisticated control over these interactions requires reducing or preventing non-specific interactions on the one hand and displaying highly specific signals that can be recognized by extracellular receptors on the other. We have recently developed ultra-low fouling coatings that can be applied in a single step using photoreactive copolymers of 2-hydroxypropyl acrylamide and N-benzophenone acrylamide. Here, we have expanded this approach by incorporating polymerizable peptide monomers into these copolymers. The monomers QQGWFGAGK(acrylamide) and acrylamide-GAGQQGWF were synthesized after identifying the QQGWF sequence as a binding motif for CD44 by phage display for the first time. Our results demonstrate that UV-crosslinked coatings fabricated using the QQGWFGAGK(acrylamide) monomer are effective at selectively binding hMSC in the presence of HepG2 and HEK293 cells due to the difference in CD44 expression. Our results also demonstrate that the peptide modified coatings retain their low biofouling character using a BCA protein binding assay as well as an E. coli bacterial attachment assay over a 24 h period. Our approach provides an alternative to traditional integrin-mediated selective cell binding on surfaces and opens the door to new diagnostic applications, exploiting the fact that the transmembrane protein CD44 is highly expressed in multiple diseases.

The binding of boronated peptides to low affinity mammalian saccharides

A 54-member library of boronated octapeptides, with all but the boronated residue being proteinogenic, was tested for affinity to a set of saccharides commonly found on the terminus of mammalian glycans. After experimentation with a high-throughput dye-displacement assay, attention was focused on isothermal titration calorimetry as a tool to provide reliable affinity data, including enthalpy and entropy of binding. A small number of boronated peptides showed higher affinity and significant selectivity for N-acetylneuraminic acid over methyl-α-d-galactopyranoside, methyl-α/β-l-fucopyranoside and N-acetyl-d-glucosamine. Thermodynamic data showed that for most of the boronated peptides studied, saccharide binding was associated with a significant increase in entropy, presumably resulting from the displacement of semiordered water molecules from around the sugar and/or peptide.

Effect of the stiffness of bone substitutes on the biomechanical behaviour of femur for core decompression

Core decompression is the most common procedure for treatment of the early stages of osteonecrosis of the femoral head. The purpose of this study was to compare the biomechanical performance of four different bone graft substitutes combined with core decompression. Subject-specific finite element models generated from computed tomography (CT) scan data were used for a comprehensive analysis. Two different contact conditions were simulated representing states of osseointegration at the interface. Our results showed that the use of a low-stiffness bone substitute did not increase the risk of femoral fracture in the early postoperative phase, but resulted in less micromotion and interfacial stresses than high-stiffness bone substitutes.

Glycodendropeptides stimulate dendritic cell maturation and T cell proliferation: a potential influenza A virus immunotherapy

A GDP displaying the NP_366–374 influenza A virus epitope induces an immunostimulatory effect, emerging as a potential flu vaccine.

Experimental and computational studies on the femoral fracture risk for advanced core decompression

BACKGROUND

Two questions are often addressed by orthopedists relating to core decompression procedure: 1) Is the core decompression procedure associated with a considerable lack of structural support of the bone? and 2) Is there an optimal region for the surgical entrance point for which the fracture risk would be lowest? As bioresorbable bone substitutes become more and more common and core decompression has been described in combination with them, the current study takes this into account.

METHODS

Finite element model of a femur treated by core decompression with bone substitute was simulated and analyzed. In-vitro compression testing of femora was used to confirm finite element results.

FINDINGS

The results showed that for core decompression with standard drilling in combination with artificial bone substitute refilling, daily activities (normal walking and walking downstairs) are not risky for femoral fracture. The femoral fracture risk increased successively when the entrance point is located further distal. The critical value of the deviation of the entrance point to a more distal part is about 20mm.

INTERPRETATION

The study findings demonstrate that optimal entrance point should locate on the proximal subtrochanteric region in order to reduce the subtrochanteric fracture risk. Furthermore the consistent results of finite element and in-vitro testing imply that the simulations are sufficient.

Intracellular nucleic acid delivery by the supercharged dengue virus capsid protein

Supercharged proteins are a recently identified class of proteins that have the ability to efficiently deliver functional macromolecules into mammalian cells. They were first developed as bioengineering products, but were later found in the human proteome. In this work, we show that this class of proteins with unusually high net positive charge is frequently found among viral structural proteins, more specifically among capsid proteins. In particular, the capsid proteins of viruses from the Flaviviridae family have all a very high net charge to molecular weight ratio (> +1.07/kDa), thus qualifying as supercharged proteins. This ubiquity raises the hypothesis that supercharged viral capsid proteins may have biological roles that arise from an intrinsic ability to penetrate cells. Dengue virus capsid protein was selected for a detailed experimental analysis. We showed that this protein is able to deliver functional nucleic acids into mammalian cells. The same result was obtained with two isolated domains of this protein, one of them being able to translocate lipid bilayers independently of endocytic routes. Nucleic acids such as siRNA and plasmids were delivered fully functional into cells. The results raise the possibility that the ability to penetrate cells is part of the native biological functions of some viral capsid proteins.

Chimeric infectious bursal disease virus-like particles as potent vaccines for eradication of established HPV-16 E7-dependent tumors

Cervical cancer is caused by persistent high-risk human papillomavirus (HR-HPV) infection and represents the second most frequent gynecological malignancy in the world. The HPV-16 type accounts for up to 55% of all cervical cancers. The HPV-16 oncoproteins E6 and E7 are necessary for induction and maintenance of malignant transformation and represent tumor-specific antigens for targeted cytotoxic T lymphocyte–mediated immunotherapy. Therapeutic cancer vaccines have become a challenging area of oncology research in recent decades. Among current cancer immunotherapy strategies, virus-like particle (VLP)–based vaccines have emerged as a potent and safe approach. We generated a vaccine (VLP-E7) incorporating a long C-terminal fragment of HPV-16 E7 protein into the infectious bursal disease virus VLP and tested its therapeutic potential in HLA-A2 humanized transgenic mice grafted with TC1/A2 tumor cells. We performed a series of tumor challenge experiments demonstrating a strong immune response against already-formed tumors (complete eradication). Remarkably, therapeutic efficacy was obtained with a single dose without adjuvant and against two injections of tumor cells, indicating a potent and long-lasting immune response.

Azole antimycotics--a highway to new drugs or a dead end?

Azole antimycotics are a well-known and important class of agents that are used in hospital practice, everyday health care, veterinary medicine and for crop protection. The era of azole fungicides began with the breakthrough of chlormidazole roughly 50 years ago. Since then, more than 20 drugs of this group, including triazoles, have been brought to the market. The specific chemical structure and mechanism of the action of azoles along with the eukaryotic character of fungal pathogens raise several serious issues. Resistance to drugs and disturbance to metabolic pathways are among the most important. On the other hand, these same features are responsible for unique and novel applications of these drugs. As a result, old and ineffective antifungal drugs can be successfully used in the treatment of parasitic diseases, bacterial infections or cancers. Are azoles getting their second wind?

Reverse thioether ligation route to multimeric peptide antigens

Multimeric presentation, a rather effective way of enhancing peptide immunogenicity, is best exemplified by MAP (multiple antigenic peptide) dendrimers consisting of a branched Lys core on which several copies of the peptide epitope are displayed. While accessible by solid-phase synthesis, MAPs can also be conveniently made in solution, e.g., by linking the epitope (N-acetylated and with a C-terminal Cys) through a thioether bond onto the α and ε (haloacetyl-activated) positions of the Lys core. We now report the reverse version of this approach, whereby a chloroacetyl-derivatised epitope is tethered to a thiol-functionalised form of a Lys dendron core. This convergent approach can be carried out either in solution or in the solid phase and is advantageous because (i) in situ tris(2-carboxyethyl)phosphine (TCEP)-mediated reduction of disulfide bonds maintains the thiol platform reactive throughout the ligation process; (ii) the low amounts of TCEP used pose minimal risk to chloroacetyl groups in the peptide, resulting in (iii) significantly reduced byproduct formation, hence cleaner products. For the solid phase version of the method, an optimised procedure has been devised to convert the Lys core into a tetrathiol dendron.

Selenomethionine incorporation into amyloid sequences regulates fibrillogenesis and toxicity

Background

The capacity of a polypeptide chain to engage in an amyloid formation process and cause a conformational disease is contained in its sequence. Some of the sequences undergoing fibrillation contain critical methionine (Met) residues which in vivo can be synthetically substituted by selenomethionine (SeM) and alter their properties.

Methodology/Principal Findings

Using peptide synthesis, biophysical techniques and cell viability determinations we have studied the effect of the substitution of methionine (Met) by selenomethionine (SeM) on the fibrillogenesis and toxic properties of Aβ40 and HuPrP(106–140). We have found that the effects display site-specificity and vary from inhibition of fibrillation and decreased toxicity ([SeM³⁵]Aβ40, [SeM¹²⁹]HuPrP(106–140) and [SeM¹³⁴]HuPrP(106–140)), retarded assembly, modulation of polymer shape and retention of toxicity ([SeM¹¹²]HuPrP(106–140) to absence of effects ([SeM¹⁰⁹]HuPrP(106–140)).

Conclusions/Significance

This work provides direct evidence that the substitution of Met by SeM in proamyloid sequences has a major impact on their self-assembly and toxic properties, suggesting that the SeM pool can play a major role in dictating the allowance and efficiency of a polypeptide chain to undergo toxic polymerization.

Escherichia coli cell surface perturbation and disruption induced by antimicrobial peptides BP100 and pepR

The potential of antimicrobial peptides (AMPs) as an alternative to conventional therapies is well recognized. Insights into the biological and biophysical properties of AMPs are thus key to understanding their mode of action. In this study, the mechanisms adopted by two AMPs in disrupting the gram-negative Escherichia coli bacterial envelope were explored. BP100 is a short cecropin A-melittin hybrid peptide known to inhibit the growth of phytopathogenic gram-negative bacteria. pepR, on the other hand, is a novel AMP derived from the dengue virus capsid protein. Both BP100 and pepR were found to inhibit the growth of E. coli at micromolar concentrations. Zeta potential measurements of E. coli incubated with increasing peptide concentrations allowed for the establishment of a correlation between the minimal inhibitory concentration (MIC) of each AMP and membrane surface charge neutralization. While a neutralization-mediated killing mechanism adopted by either AMP is not necessarily implied, the hypothesis that surface neutralization occurs close to MIC values was confirmed. Atomic force microscopy (AFM) was then employed to visualize the structural effect of the interaction of each AMP with the E. coli cell envelope. At their MICs, BP100 and pepR progressively destroyed the bacterial envelope, with extensive damage already occurring 2 h after peptide addition to the bacteria. A similar effect was observed for each AMP in the concentration-dependent studies. At peptide concentrations below MIC values, only minor disruptions of the bacterial surface occurred.

Structure-activity relationship of CART (cocaine- and amphetamine-regulated transcript) peptide fragments

CART (cocaine- and amphetamine-regulated transcript) peptides are neuropeptides abundant in the central nervous system and periphery found to be involved in the regulation of food intake behavior and other physiological processes. Recently, we reported specific binding of (125)I-CART(61-102) to the rat adrenal pheochromocytoma cell line PC12, both intact cells and cell membranes. In this study, several fragments of CART(61-102) corresponding to its structural loops were synthesized and tested for their potency in binding experiments using PC12 intact cells and cell membranes and in feeding test with fasted mice. From all shorter peptides tested, only CART(74-86) and CART(62-86) containing disulfide bridges kept partial binding potency of the original molecule with K(i) in 10(-5) and 10(-4)M range. However, these fragments were not able to inhibit food intake after their central administration up to a dose of 4 nmol/mouse. The results showed that a compact structure containing three disulfide bridges is necessary for preservation of full biological activity of CART peptides.

The effects of N-terminal part modification of arginine vasopressin analogues with 2-aminoindane-2-carboxylic acid: a highly potent V2 agonist

In this study we present the synthesis and some pharmacological properties of nine new analogues of arginine vasopressin modified in the N-terminal part of the molecule with 2-aminoindane-2-carboxylic acid (Aic). The peptides were tested for their in vitro uterotonic and in vivo pressor and antidiuretic activities. One of the new peptides, [Mpa1,Aic2,Val4,D-Arg8]VP, exhibited an antidiuretic activity similar to that of [Mpa1,D-Arg8]VP, thus being one of the most potent antidiuretic vasopressin analogues reported to date.

Sequencing batch reactor (SBR) as optimal method for production of granular activated sludge (GAS)--fluid dynamic investigations

Fluid dynamic investigations of multiphase flow (fluid, air, granules) in a sequencing batch reactor (SBR) are presented. SBR can be considered as an attractive technology for cultivation of granular activated sludge (GAS). Granulation is a complicated process and its mechanism is not fully understood yet. Many factors influence the formation and structure of aerobic granular sludge in a bioreactor. Extracellular polymer substances (EPS) and superficial gas velocity (SGV) play a crucial role for granules formation. Additionally, it is supposed that EPS production is stimulated by mechanical forces. It is also assumed that hydrodynamic effects have a major influence on the formation, shape and size of GAS in SBR under aerobic condition. However, the influence of stress on granulation is poorly investigated. Thus, in the present paper, fluid dynamic investigations of multiphase flow in a SBR, particularly effect of normal and shear strain, are reported. In order to analyse multiphase flow in the SBR, optical in-situ techniques with particle image velocimetry (PIV) and particle tracking velocimetry (PTV) are implemented. Obtained results show a characteristic flow pattern in a SBR. It is pointed out that additional effects like particle-wall collisions, inter particle collisions, erosion can also affect significantly granules formation.

Analogues of neurohypophyseal hormones, oxytocin and arginine vasopressin, conformationally restricted in the N-terminal part of the molecule

It is generally accepted that the conformation of the N-terminal part of neurohypophyseal hormones analogues is important for their pharmacological activity. In this work, we decided to investigate how the substitution of positions 2 and 3 with the ethylene-bridged dipeptide would alter the pharmacological properties of OT, [Mpa1]OT, and [Cpa1]OT (OT=oxytocin; Mpa=3-mercaptopropionic acid; Cpa=1-mercaptocyclohexaneacetic acid) and to investigate how a bulky 3,3-diphenyl-L-alanine residue incorporated in position 2 of AVP, [Mpa1]AVP, and [Cpa1]AVP (AVP=arginine vasopressin) would change the pharmacological profile of the compounds. The next analogues, [Val4]AVP, [Mpa1,Val4]AVP, and [Cpa1,Val4]AVP, had N-benzyl-L-alanine introduced at position 3. The last peptide was designed by Cys1 substitution in AVP by its sterically restricted bulky counterpart, alpha-hydroxymethylcysteine. All the peptides were tested for their in vitro uterotonic, pressor, and antidiuretic activities in the rat. The results of these assays showed that the reduction of conformational freedom of the N-terminal part of the molecule had a significant impact on pharmacological activities.

New bradykinin analogues substituted in positions 7 and 8 with sterically restricted 1-aminocyclopentane-1-carboxylic acid

A sterically constrained non-coded amino acid, 1-aminocyclopentane-1-carboxylic acid (Apc), was introduced in position 7 or 8 of the bradykinin (BK) B(2) receptor antagonist, [D-Arg(0), Hyp(3), Thi(5, 8), D-Phe(7)]BK, previously synthesized by Stewart's group. This modification is believed to reduce the flexibility of the peptides, thereby forcing the peptide backbone and side chains to adopt specific orientations. Apc substitution was combined with acylation of the N-terminus with 1-adamantaneacetic acid (Aaa). The activity of four new analogues was assayed in isolated rat uterus and in rat blood pressure tests. The results clearly demonstrated that the Apc residue inserted in position 7 led to a reduction of antagonistic properties in the rat uterus assay or even restored the agonism in the blood pressure test, whereas Apc at position 8 enhanced antagonistic potency in both the tests. In both cases, acylation of the N-terminus led to the enhancement of the antagonistic potency. On the basis of these findings, new potent and selective B(2) blockers might be designed.

New Bradykinin Analogues Modified in the C-Terminal Part with Sterically Restricted 1-Aminocyclohexane-1-carboxylic Acid

In the present work, a sterically constrained noncoded amino acid, 1-aminocyclohexane-1-carboxylic acid (Acc), was substituted in position 8 of the peptide chain of bradykinin (BK) and position 6, 7, or 8 of its B2 receptor antagonist [D-Arg0,Hyp3,Thi,(5,8)D-Phe7]BK, previously synthesized by Stewart's group, to reduce the flexibility of the peptides, thus forcing the peptide backbone and side chains to adopt specific orientations. Knowing that acylation of the N-terminus of several known B2 blockers with a variety of bulky groups has consistently improved their antagonistic potency in the rat blood pressure assay, the Acc substituted analogues were also synthesized in the N-acylated form with 1-adamantaneacetic acid (Aaa). The activity of eight new analogues was assayed in isolated rat uterus and in rat blood pressure tests. The results clearly demonstrated the importance of the position in the peptide chain into which the sterically restricted Acc residue was inserted. Meanwhile, Acc at positions 6 and 7 led to reduction of antagonistic qualities or even restored the agonism, respectively. Acc at position 8 enhanced antagonistic qualities in both tests. The Acc at position 8 of BK strongly reduced the agonistic potency. In most cases acylation of the N-terminus led either to enhancement of antagonistic potencies or to further decrease of agonistic potency. Our findings offer new possibilities for designing new potent and selective B2 blockers.

Analogues of arginine vasopressin and its agonist and antagonist modified in the N-terminal part of the molecule with l-beta-homophenylalanine

In continuation of our efforts to elucidate the role of positions 2 and 3 in arginine vasopressin (AVP) and its analogues, we designed and synthesized peptides modified in these positions with l-beta-homophenylalanine (beta-Hph). Two of them had just this single modification, the next two peptides are analogues of the V2 agonist, namely [3-mercaptopropionic acid (Mpa)1]AVP (dAVP). The last two compounds were designed by substitution of positions 2 or 3 of a potent V(1a) antagonist, [1-mercaptocyclohexaneacetic acid (Cpa)1]AVP, with beta-Hph. All the peptides were tested for their pressor and antidiuretic and uterotonic in vitro activities in the rat. All the activities tested have been found to be significantly decreased. Three analogues, i.e. [Mpa(1),beta-Hph2]AVP, [Cpa1,beta-Hph2]AVP, [Cpa1,beta-Hph3]AVP, turned out to be uterotonic antagonists with pA2 = 6.3 +/- 0.2, 6.3 +/- 0.1, 6.0 +/- 0.3 respectively. The last one exhibited antipressor properties also (pA2 = 6.4 +/- 0.1).

New acylated bradykinin analogues: effect on rat blood pressure and rat uterus

It was previously reported that acylation of the N-terminus of several known B(2) antagonists with various types of bulky acyl groups consistently improved their antagonistic potency in the rat blood pressure assay. On the other hand, earlier results seem to suggest that the effects of acylation on the contractility of isolated rat uterus depend substantially on the chemical character of the acyl group, as it was observed that this modification may either change the range of antagonism or even transform it into agonism. Bearing all this in mind, three new analogues of bradykinin were designed by modifying the moderately potent B(2) antagonist, previously synthesized by Stewart's group, D-Arg-Arg-Pro-Hyp-Gly-Thr-Ser-D-Phe-Thi-Arg. New analogues were obtained by acylation of the N-terminus of the above peptide with succinic acid, 12-aminododecanoic acid and 4-aminobenzoic acid in order to confirm whether either the positive or the negative charge on the N-terminal end of the peptide is responsible for the transformation of activity. The activity of analogues was assessed on blood pressure and in uterotonic in vitro tests. The modifications proposed either preserved or increased the antagonistic potency in the rat blood pressure test. On the other hand, the three substituents, depending on their chemical character, differently influenced the interaction with the rat uterine receptors. The results may be of value in the design of new B(2) agonists and antagonists.

Analogues of arginine vasopressin modified in position 2 and 3 with conformationally constrained dipeptide fragments

This study describes the synthesis and some pharmacological properties of ten new analogues of arginine vasopressin (AVP) containing a conformationally constrained dipeptide fragment in the N-terminal part of their molecules. Amino acid residues in positions 2 and 3 of AVP and some of its agonistic analogues were replaced with -Phe-Phe and D-Phe-D-Phe, dipeptides having a -CH2-CH2- link bridging two nitrogens. All the new peptides were tested for vasopressor and antidiuretic activities. Four peptides with pA2 values ranging from 5.96 to 7.21 turned out to be weak or moderately potent V1a antagonists. The results supplied new information about the structure-activity relationship of AVP analogues. As some of these were unexpected, they point to the need for caution when extrapolating previously known effects of modifications to analogues having conformationally constrained fragments in their molecules.

Investigation ofcis/trans ratios of peptide bonds in AVP analogues containingN-methylphenylalanine enantiomers

The solution conformation of vasopressin analogues, modified at positions 2 and 3 with N-methylphenylalanine or its enantiomer, [D-MePhe2,MePhe3]AVP and [MePhe2,D-MePhe3]AVP, were studied by 2D NMR spectroscopy in H2O/D2O and theoretical calculations (EDMC/ANALYZE). In the case of [MePhe2,D-MePhe3]AVP, the synthesis afforded two products, A and B, which had identical molecular ions and similar retention times on HPLC. This finding was explained by racemization of Cys1, which gave an additional analogue, [D-Cys1,MePhe2,D-MePhe3]AVP (B). The possibility is not excluded of racemization of Cys1 in the remaining analogues of this series. However, only in the case of [MePhe2,D-MePhe3]AVP was this process so distinct that two strong peaks in the HPLC chromatogram were observed. The NMR spectra of all the analogues showed several distinct sets of residual proton resonances. This suggests that the peptides adopt more than two groups of conformations in H2O/D2O. This fact is due to cis/trans isomerization. Two more populated isomers arise from the cis/trans isomerization across the 2-3 peptide bond in [D-MePhe2,MePhe3]AVP and [MePhe2,D-MePhe3]AVP (A) and across the 1-2 peptide bond in [D-Cys1,MePhe2,D-MePhe3]AVP (B).

Influence of enantiomers of 1-naphthylalanine in position 2 of VAVP and dVAVP on their pharmacological properties

In this study, we described the synthesis and some pharmacological properties of four new analogues of arginine vasopressin (AVP). Two peptides are substituted in position 2 with L-1-naphthylalanine (L-1-Nal) or its D-enantiomer and in position 4 with valine. In the further two compounds, we combined the above modifications with placement into position 1 of 3-mercaptopropionic acid residue (Mpa). All new peptides were tested for vasopressor and antidiuretic activities. We also estimated the uterotonic activities of these compounds in vitro. Urine samples prior and after peptide administration were analyzed for electrolytes excretion. All analogues are potent oxytocin antagonists. One of them, namely [L-1-Nal2,Val4]AVP, which appears practically not to interact with V1a and V2 receptors, is exceptionally selective. Our results open new possibilities for the design of very potent and selective oxytocin antagonists in vitro.

The influence of 1-aminocyclopentane-1-carboxylic acid at position 2 or 3 of AVP and its analogues on their pharmacological properties

This study describes the synthesis and some pharmacological properties of eight new analogues of arginine vasopressin (AVP) substituted at position 2 or 3 with cycloleucine (1-aminocyclopentane-1-carboxylic acid, Apc). All new peptides were tested for their pressor, antidiuretic and uterotonic in vitro potency. The Apc3 modification resulted in an almost complete loss of potency in all three tests, which is interpreted as a loss of interaction with all three neurohypophyseal hormone receptors. On the other hand, the Apc2 modification resulted in compounds having differently modified activities (high antidiuretic potency, low and graded pressor activity and either no activity or low oxytocin antagonizing activity in the uterotonic in vitro test) thus selectively altering the interaction with the receptors similar to that of 1-aminocyclohexane-1-carboxylic acid (Acc). The results obtained may be helpful for designing new analogues of arginine vasopressin.

Cis/trans conformational equilibrium across the N-methylphenylalanine- N-methylphenylalanine peptide bond of arginine vasopressin analogs

Two cyclic analogs of vasopressin, -Pro-Arg-Gly-NH(2) (1) and -Pro-Arg-Gly-NH(2) (2) were synthesized by the solid phase method. Their structure was determined in aqueous solution by two-dimensional NMR techniques and simulated annealing algorithm from an extended template in X-PLOR. The total chemical shift correlation spectroscopy and rotating-frame Overhauser enhancement spectroscopy of the peptides displayed four distinct sets of residual proton resonances. This suggests that both analogs adopt four families of conformations in H(2)O/D(2)O (9 : 1) (one major and three minor species). In further analysis only signals of major species (M) and of one minor species (m(1)) were considered. The major species of both peptides include a trans peptide bond between the first and second residue, and a cis form between the second and third residue. In the minor species, all peptide bonds were found to exist in trans geometry.

Highly Potent 1-Aminocyclohexane-1-Carboxylic Acid Substituted V2 Agonists of Arginine Vasopressin

The synthesis and some pharmacological properties of two sets of analogues, one consisting of six peptides with 1-aminocyclohexane-1-carboxylic acid (Acc) in position 2 and the other with the amino acid in position 3, have been described. All the peptides were tested for their pressor, antidiuretic, and uterotonic in vitro activities. The Acc(2) modification has been shown to selectively modulate the activities of the analogues. Four of the compounds were highly potent antidiuretic agonists with different pressor and uterotonic activities. On the other hand, the 3-substituted counterparts failed to exhibit any of the activities. One exception was provided by the [Mpa(1),Acc(3),Val(4),D-Arg(8)]VP analogue, which exhibited antidiuretic activity matching that of AVP, yet, unlike AVP, it was fairly selective.

Analogues of arginine vasopressin modified in the N-terminal part of the molecule with enantiomers of N-methylphenylalanine

Four new analogues of arginine vasopressin (AVP) substituted in positions 2 and 3 with all possible combinations of enantiomers of N-methylphenylalanine were synthesized and studied to assess the influence of N-methylation of the peptide bonds between the first three amino acids on the pharmacological properties of the resulting peptides. The next three analogues were designed to learn how the shortening of the peptide chain, by removal of one of the N-methylphenylalanine residues, would affect pharmacological properties of the resulting compounds. The activity of the analogues was tested in the in vitro uterotonic, pressor and antidiuretic tests. None of the prepared analogues displayed significant biological activity with the exception of [Me-d-Phe(2), Me-Phe(3)]AVP and [Me-d-Phe(2,3)]AVP, which showed low antiuterotonic activity (pA(2) = 6.6 and pA(2) = 6.4, respectively). Our results, while not impressive in terms of biological activity, may be helpful for designing potent and selective oxytocin antagonists.

Potent bradykinin antagonists containing N-benzylglycine or N-benzyl-l-alanine in position 8

Two new analogues of a previously designed bradykinin (BK) antagonist, d-Arg-Arg-Pro-Hyp-Gly-Thi-Ser-d-Phe-Thi-Arg, substituted in position 8 by N-benzylglycine and N-benzyl-l-alanine were designed, synthesized and bioassayed. The results show an impressive enhancement of B2 antagonistic potencies of both peptides in comparison with the model. In two further analogues these modifications were combined with acylation of the N-terminus with 1-adamantanacarboxylic acid. Acylated analogues exhibited higher antagonistic potency in comparison with the parent compounds, however, the range of effect was not as high as in previously described cases. The activity of analogues was assessed by their ability to inhibit vasodepressor response to exogenous BK (rat blood pressure test). Our results may be of value in the design of more potent BK antagonists.

Influence of 1-aminocyclohexane-1-carboxylic acid in position 2 or 3 of AVP and its analogues on their pharmacological properties

In this study we describe the synthesis and some pharmacological properties of seven new analogues of arginine vasopressin (AVP) substituted in position 2 or 3 with 1-aminocyclohexane-1-carboxylic acid (Acc). All peptides were tested for the pressor, antidiuretic and uterotonic in vitro activities. The Acc3 modifications of AVP, dAVP, [d-Arg8]VP and [Cpa1]AVP have been found to be deleterious for interaction with all three neurohypophyseal hormone receptors, as judged from the several orders of magnitude decreased biological activities, whereas Acc2 substitution selectively altered the interaction with the receptors. Two of the new analogues, [Acc2]AVP and [Acc2, d-Arg8]AVP, are potent antidiuretic agonists. [Acc2]AVP exhibits moderate pressor agonistic activity and weak antiuterotonic properties. [Acc2, d-Arg8]AVP has been found to be a weak antagonist in the pressor and uterotonic tests. Another analogue - [Cpa1, Acc3]AVP - turned out to be a highly selective V2 agonist. This is an unexpected effect, as its parent peptide, [Cpa1]AVP is a very potent V1a receptor antagonist. This is the first Cpa1 modification to have resulted in V2 agonism enhancement. Besides providing useful information about structure-activity relationships, our results could open up new possibilities in the design of highly potent and selective V2 agonists.

Phosphorylation of acidic ribosomal proteins by ribosome-associated protein kinases of Saccharomyces cerevisiae and Schizosaccharomyces pombe

Two proteins of 13 kDa and 38 kDa, the components of 60S ribosomal subunits, were identified as phosphorylation substrates for protein kinases tightly associated with S. cerevisiae and Schizosaccharomyces pombe ribosomes. An enzyme with properties of multifunctional casein kinase II was detected in ribosome preparations from both yeast species. In S. cerevisiae another protein kinase with high substrate specificity toward those proteins was also identified. By using isoelectric focusing, the protein band of 13 kDa from S. cerevisiae and S. pombe was resolved respectively into three and four major forms of different charge. The same protein forms were phosphorylated in the in vivo 32P-labelling experiments.

Sensitivity of the replica method in the detection of candidal infection among denture wearers with clinically healthy oral mucosa

To ascertain the role of Candida in denture stomatitis, the practitioner must conduct a mycologic examination of the acrylic resin denture surface, because it acts as a reservoir for continuous reinfection of the palate. Twenty-two patients were examined to compare the sensitivity of the standard technique of swabbing the denture to that of a newly developed cast agar replica technique for detecting Candida albicans. The dentures were swabbed and cast replicas of the tissue-fitting surface of the dentures were made of both study populations. The majority of cultures obtained by swabbing failed to detect the presence of Candida albicans, while all cast agar replicas grew Candida albicans. The replica method for the detection of Candida albicans in edentulous patients seemed to be a more sensitive method than currently available mycologic methods.