15 research outputs found
Enantioseparation of ß-amino acids by liquid chromatography using core-shell chiral stationary phases based on teicoplanin and teicoplanin aglycone
The Role of VEGF Receptors as Molecular Target in Nuclear Medicine for Cancer Diagnosis and Combination Therapy
One approach to anticancer treatment is targeted anti-angiogenic therapy (AAT) based on prevention of blood vessel formation around the developing cancer cells. It is known that vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptors (VEGFRs) play a pivotal role in angiogenesis process; hence, application of angiogenesis inhibitors can be an effective approach in anticancer combination therapeutic strategies. Currently, several types of molecules have been utilised in targeted VEGF/VEGFR anticancer therapy, including human VEGF ligands themselves and their derivatives, anti-VEGF or anti-VEGFR monoclonal antibodies, VEGF binding peptides and small molecular inhibitors of VEGFR tyrosine kinases. These molecules labelled with diagnostic or therapeutic radionuclides can become, respectively, diagnostic or therapeutic receptor radiopharmaceuticals. In targeted anti-angiogenic therapy, diagnostic radioagents play a unique role, allowing the determination of the emerging tumour, to monitor the course of treatment, to predict the treatment outcomes and, first of all, to refer patients for AAT. This review provides an overview of design, synthesis and study of radiolabelled VEGF/VEGFR targeting and imaging agents to date. Additionally, we will briefly discuss their physicochemical properties and possible application in combination targeted radionuclide tumour therapy
Interactions of Linear Analogues of Battacin with Negatively Charged Lipid Membranes
The increasing resistance of bacteria to available antibiotics has stimulated the search for new antimicrobial compounds with less specific mechanisms of action. These include the ability to disrupt the structure of the cell membrane, which in turn leads to its damage. In this context, amphiphilic lipopeptides belong to the class of the compounds which may fulfill this requirement. In this paper, we describe two linear analogues of battacin with modified acyl chains to tune the balance between the hydrophilic and hydrophobic portion of lipopeptides. We demonstrate that both compounds display antimicrobial activity with the lowest values of minimum inhibitory concentrations found for Gram-positive pathogens. Therefore, their mechanism of action was evaluated on a molecular level using model lipid films mimicking the membrane of Gram-positive bacteria. The surface pressure measurements revealed that both lipopeptides show ability to bind and incorporate into the lipid monolayers, resulting in decreased ordering of lipids and membrane fluidization. Atomic force microscopy (AFM) imaging demonstrated that the exposure of the model bilayers to lipopeptides leads to a transition from the ordered gel phase to disordered liquid crystalline phase. This observation was confirmed by attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) results, which revealed that lipopeptide action causes a substantial increase in the average tilt angle of lipid acyl chains with respect to the surface normal to compensate for lipopeptide insertion into the membrane. Moreover, the peptide moieties in both molecules do not adopt any well-defined secondary structure upon binding with the lipid membrane. It was also observed that a small difference in the structure of a lipophilic chain, altering the balance between hydrophobic and hydrophilic portion of the molecules, results in different insertion depth of the active compounds
Synthesis, Physicochemical and Biological Study of Gallium-68- and Lutetium-177-Labeled VEGF-A<sub>165</sub>/NRP-1 Complex Inhibitors Based on Peptide A7R and Branched Peptidomimetic
Neuropilin-1 (NRP-1) is a surface receptor found on many types of cancer cells. The overexpression of NRP-1 and its interaction with vascular endothelial growth factor-165 (VEGF165) are associated with tumor growth and metastasis. Therefore, compounds that block the VEGF165/NRP-1 interaction represent a promising strategy to image and treat NRP-1-related pathologies. The aim of the presented work was to design and synthesize radioconjugates of two known peptide-type inhibitors of the VEGF165/NRP-1 complex: A7R peptide and its shorter analog, the branched peptidomimetic Lys(hArg)-Dab-Pro-Arg. Both peptide-type inhibitors were coupled to a radionuclide chelator (DOTA) via a linker (Ahx) and so radiolabeled with Ga-68 and Lu-177 radionuclides, for diagnostic and therapeutic uses, respectively. The synthesized radioconjugates were tested for their possible use as theranostic-like radiopharmaceuticals for the imaging and therapy of cancers that overexpress NRP-1. The obtained results indicate good efficiency of the radiolabeling reaction and satisfactory stability, at least 3t1/2 for the 68Ga- and 1t1/2 for the 177Lu-radiocompounds, in solutions mimicking human body fluids. However, enzymatic degradation of both the studied inhibitors caused insufficient stability of the radiocompounds in human serum, indicating that further modifications are needed to sufficiently stabilize the peptidomimetics with inhibitory properties against VEGF165/NRP-1 complex formation
Comparison of the separation performances of cinchona alkaloid-based zwitterionic stationary phases in the enantioseparation of β2- And β3-amino acids
Comparison of the Separation Performances of Cinchona Alkaloid-Based Zwitterionic Stationary Phases in the Enantioseparation of β2- and β3-Amino Acids
The enantiomers of twelve unusual β2- and β3-homoamino acids containing the same side-chains were separated on chiral stationary phases containing a quinine- or quinidine-based zwitterionic ion-exchanger as chiral selector. The effects of the mobile phase composition, the nature and concentration of the acid and base additives and temperature on the separations were investigated. The changes in standard enthalpy, ∆(∆H°), entropy, ∆(∆S°), and free energy, ∆(∆G°), were calculated from the linear van’t Hoff plots derived from the ln α vs. 1/T curves in the studied temperature range (10–50 °C). The values of the thermodynamic parameters depended on the nature of the selectors, the structures of the analytes, and the positions of the substituents on the analytes. A comparison of the zwitterionic stationary phases revealed that the quinidine-based ZWIX(−)™ column exhibited much better selectivity for both β2- and β3-amino acids than the quinine-based ZWIX(+)™ column, and the separation performances of both the ZWIX(+)™ and ZWIX(−)™ columns were better for β2-amino acids. The elution sequence was determined in some cases and was observed to be R < S and S < R on the ZWIX(+)™ and ZWIX(−)™ columns, respectively
Modulation of Activity of Ultrashort Lipopeptides toward Negatively Charged Model Lipid Films
Because
of the increasing resistance of pathogens to commonly used
antibiotics, there is an urgent need to find alternative antimicrobial
compounds with different mechanisms of action. Among them, lipopeptides
are recognized as promising candidates. In this work, the Langmuir
technique and atomic force microscopy were employed to investigate
the interactions of two novel lipopeptides with negatively charged
phospholipid membranes, which served as a simplified model of inner
membrane of Gram-negative bacteria. Lipid films contained phosphatidylethanolamine
and phosphatidylglycerol extracts from E. coli bacteria. Lipopeptides were composed of palmitoyl chain covalently
coupled to N-terminus of peptide with Trp-Lys-Leu-Lys amino acid sequence
and the conformation of third residue was either d-Leu or l-Leu. It was found that chirality of leucine strongly affects
interfacial behavior of these compounds, which was ascribed to the
difference in effective size of the peptide portion of the molecules.
Although the lipopeptides were the same in terms of amino acid sequence,
charge, and identity of lipophilic chain, the experiments revealed
that the barrier for their insertion into the lipid membrane is significantly
different. Namely, it was lower for lipopeptide containing d-Leu residue. We have also found that insertion of the lipopeptides
into the model membranes strongly alters lateral distribution of the
membrane components and leads to its substantial fluidization. The
dynamics of reorganization was noticeably faster in the presence of
lipopeptide with smaller size of peptide moiety, i.e., containing d-Leu. It proves that effective size of the peptide headgroup
is an important factor determining lipopeptide activity toward the
lipid membranes
Enantioseparation of β2-amino acids on cinchona alkaloid-based zwitterionic chiral stationary phases. Structural and temperature effects
Scandium-44 Radiolabeled Peptide and Peptidomimetic Conjugates Targeting Neuropilin-1 Co-Receptor as Potential Tools for Cancer Diagnosis and Anti-Angiogenic Therapy
Pathological angiogenesis, resulting from an imbalance between anti- and pro-angiogenic factors, plays a pivotal role in tumor growth, development and metastasis. The inhibition of the angiogenesis process by the VEGF/VEGFR-2/NRP-1 pathway raises interest in the search for such interaction inhibitors for the purpose of the early diagnosis and treatment of angiogenesis-dependent diseases. In this work we designed and tested peptide-based radiocompounds that selectively bind to the neuropilin-1 co-receptor and prevent the formation of the pro-angiogenic VEGF-A165/NRP-1 complex. Three biomolecules, A7R and retro-inverso DR7A peptides, and the branched peptidomimetic Lys(hArg)-Dab-Pro-Arg (K4R), conjugated with macrocyclic chelator through two linkers’ types, were labeled with theranostic scandium-44 radionuclide, and studied in vitro as potential targeted radiopharmaceuticals. ELISA (enzyme-linked immunosorbent assay) studies showed no negative effect of the introduced biomolecules’ changes and high NRP-1 affinity in the case of A7R- and K4R-radiocompounds and a lack affinity for DR7A-radiocompounds. All radiopeptides showed a hydrophilic nature as well as high stability against ligand exchange reactions in cysteine/histidine solutions. Unfortunately, all radiocompounds showed unsatisfactory nano-scale stability in human serum, especially for use as therapeutic radioagents. Further work is ongoing and focused on the search for angiogenesis inhibitors that are more human serum stable
Amyloidogenic Properties of Short α‑l‑Glutamic Acid Oligomers
Poly-l-glutamic acid (PLGA) forms amyloid-like β<sub>2</sub>-fibrils with the main spectral component of vibrational amide
I′ band unusually shifted below 1600 cm<sup>–1</sup>. This distinct infrared feature has been attributed to the presence
of bifurcated hydrogen bonds coupling CO and N–D (N–H)
groups of the main chains to glutamate side chains. Here, we investigate
how decreasing the chain length of PLGA affects its capacity to form
β<sub>2</sub>-fibrils. A series of acidified aqueous solutions
of synthetic (l-Glu)<sub><i>n</i></sub> peptides
(<i>n</i> ≈ 200, 10, 6, 5, 4, and 3) were incubated
at high temperature. We observed that <i>n</i> = 4 is the
critical chain length for which formation of aggregates with the β<sub>2</sub>-like infrared features is still observed under such conditions.
Interestingly, according to atomic force microscopy (AFM), the self-assembly
of (l-Glu)<sub><i>n</i></sub> chains varying vastly
in length produces fibrils with rather uniform diameters of approximately
4–6 nm. Kinetic experiments on (l-Glu)<sub>5</sub> and (l-Glu)<sub>200</sub> peptides indicate that the fibrillation
is significantly accelerated not only in the presence of homologous
seeds but also upon cross-seeding, suggesting thereby a common self-assembly
theme for (l-Glu)<sub><i>n</i></sub> chains of
various lengths. Our results are discussed in the context of mechanisms
of amyloidogenic fibrillation of homopolypeptides