Peptide arrays for development of PDGFRß Affine molecules.

PURPOSE: Peptide arrays represent an attractive method for identification of amino acid motifs that bind to target structures. Spotting derivatives of the linear peptide platelet-derived growth factor receptor (PDGFR)-P1, which has been identified to bind the extracellular domain of the platelet-derived growth factor receptor beta, allows the synchronous investigation of the target affinity of numerous ligands. PROCEDURES: A peptide array randomizing PDGFR-P1 was constructed by replacement of each amino acid by all 20 natural amino acids. Incubation of the array with PDGFRß and fibroblast growth factor receptor as negative control target was performed. Selected derivatives and fragments of PDGFR-P1 were chemically synthesized, radiolabeled, and evaluated in cell-based assays, using human pancreatic carcinoma BxPC3 and human breast cancer MCF7 cells. RESULTS: Binding capacity was increased for the derivate yG2 by exchange of 7S to 7R. Competition experiments demonstrated a binding decrease with increasing competitor concentration. Serum stability of yG2 was improved compared to the native ligand. CONCLUSION: Peptide arrays were successfully applied for the improvement of the PDGFRß binding peptide PDGFR-P1.

Screening of a novel peptide targeting the proteoglycan-like region of human carbonic anhydrase IX.

The extracellular domain of human carbonic anhydrase IX (CA IX) is extended by a proteoglycan-like region (PGLR). The aim of the present study was the development of novel molecules with specificity for PGLR, which may be used for tumor targeting and imaging. PGLR was chemically synthesized, and phage display biopanning was performed. The identified ligand PGLR-P1 was labeled with 125I and characterized for target binding and metabolic stability. In vitro characterization included kinetic, competition, and internalization studies on CA IX-positive renal cell carcinoma SKRC 52 cells. The CA IX-negative cell lines HEK293 wt and BxPC3 were used as negative controls. In vitro binding experiments revealed an increasing affinity of 125I-PGLR-P1 to SKRC 52 cells but not to negative control HEK293 wt and BxPC3 cells. Internalization studies indicated an exclusive cell membrane binding. Biodistribution analysis demonstrated a higher accumulation in SKRC 52 tumors than in most normal tissues after perfusion. In vivo blocking led to a significant decrease in tumor uptake. Our findings indicate that PGLR-P1 is a promising lead structure for the development of new peptide-based ligands targeting the PGLR of CA IX and reveal challenges that need to be considered for peptide-related molecular imaging.

Collective suppression of linewidths in circuit QED.

We report the experimental observation and a theoretical explanation of collective suppression of linewidths for multiple superconducting qubits coupled to a good cavity. This demonstrates how strong qubit-cavity coupling can significantly modify the dephasing and dissipation processes that might be expected for individual qubits, and can potentially improve coherence times in many-body circuit QED.

GF-15, a novel inhibitor of centrosomal clustering, suppresses tumor cell growth in vitro and in vivo.

In contrast to normal cells, malignant cells are frequently aneuploid and contain multiple centrosomes. To allow for bipolar mitotic division, supernumerary centrosomes are clustered into two functional spindle poles in many cancer cells. Recently, we have shown that griseofulvin forces tumor cells with supernumerary centrosomes to undergo multipolar mitoses resulting in apoptotic cell death. Here, we describe the characterization of the novel small molecule GF-15, a derivative of griseofulvin, as a potent inhibitor of centrosomal clustering in malignant cells. At concentrations where GF-15 had no significant impact on tubulin polymerization, spindle tension was markedly reduced in mitotic cells upon exposure to GF-15. Moreover, isogenic cells with conditional centrosome amplification were more sensitive to GF-15 than parental controls. In a wide array of tumor cell lines, mean inhibitory concentrations (IC(50)) for proliferation and survival were in the range of 1 to 5 µmol/L and were associated with apoptotic cell death. Importantly, treatment of mouse xenograft models of human colon cancer and multiple myeloma resulted in tumor growth inhibition and significantly prolonged survival. These results show the in vitro and in vivo antitumor efficacy of a prototype small molecule inhibitor of centrosomal clustering and strongly support the further evaluation of this new class of molecules.

Nonequilibrium dynamics of coupled qubit-cavity arrays.

We study the coherence and fluorescence properties of the coherently pumped and dissipative Jaynes-Cummings-Hubbard model describing polaritons in a coupled-cavity array. At weak hopping we find strong signatures of photon blockade similar to single-cavity systems. At strong hopping the state of the photons in the array depends on its size. While the photon blockade persists in a dimer consisting of two coupled cavities, a coherent state forms on an extended lattice, which can be described in terms of a semiclassical model.

Optimization of a novel peptide ligand targeting human carbonic anhydrase IX.

BACKGROUND: Carbonic anhydrase IX (CA IX) is a hypoxia-regulated transmembrane protein over-expressed in various types of human cancer. Recently, a new peptide with affinity for human carbonic anhydrase IX (CaIX-P1) was identified using the phage display technology. Aim of the present study is to characterize the binding site in the sequence of CaIX-P1, in order to optimize the binding and metabolic properties and use it for targeting purposes. METHODOLOGY/PRINCIPAL FINDINGS: Various fragments of CaIX-P1 were synthesized on solid support using Fmoc chemistry. Alanine scanning was performed for identification of the amino acids crucial for target binding. Derivatives with increased binding affinity were radiolabeled and in vitro studies were carried out on the CA IX positive human renal cell carcinoma cell line SKRC 52 and the CA IX negative human pancreatic carcinoma cell line BxPC3. Metabolic stability was investigated in cell culture medium and human serum. Organ distribution and planar scintigraphy studies were performed in Balb/c nu/nu mice carrying subcutaneously transplanted SKRC 52 tumors. The results of our studies clearly identified amino acids that are important for target binding. Among various fragments and derivatives the ligand CaIX-P1-4-10 (NHVPLSPy) was found to possess increased binding potential in SKRC 52 cells, whereas no binding capacity for BxPC3 cells was observed. Binding of radiolabeled CaIX-P1-4-10 on CA IX positive cells could be inhibited by both the unlabeled and the native CaIX-P1 peptide but not by control peptides. Stability experiments indicated the degradation site in the sequence of CaIX-P1-4-10. Biodistribution studies showed a higher in vivo accumulation in the tumor than in most healthy tissues. CONCLUSIONS: Our data reveal modifications in the sequence of the CA IX affine ligand CaIX-P1 that might be favorable for improvement of target affinity and metabolic stability, which are necessary prior to the use of the ligand in clinical approaches.

Methyl 1-(7-acetamido-5,8-dimeth-oxy-quinolin-2-yl)-4-methyl-ß-carboline-3-carboxyl-ate.

The title compound, C(27)H(24)N(4)O(5), is an inter-mediate in the synthesis of lavendamycin via a ruthenium-catalysed [2 + 2 + 2] cyclo-addition. An intra-molecular hydrogen-bond bridge from the carboline to the quinoline stabilizes a highly planar geometry [maximum deviation = 0.065 (6) Å] for the two rigid units. This hydrogen-bond-stabilized coplanarity has a very close analogy in the structure of the anti-tumor anti-biotic streptonigrin in the solid state and in solution. Inter-molecular hydrogen-bond bridges of amides groups along the a axis and π-π stacking inter-actions [centroid-centroid distance = 3.665 (9) Å] connect mol-ecules arranged in a parallel manner.

Synthesis of ß- and γ-carbolines via ruthenium and rhodium catalysed [2+2+2] cycloadditions of yne-ynamides with methylcyanoformate.

A flexible approach towards substituted ß- and γ-carbolines based on transition metal catalysed [2+2+2] cycloaddition reactions between functionalised yne-ynamides and methylcyanoformate is described. The versatility of this new reaction sequence is demonstrated by its application in the total synthesis of the marine natural product eudistomin U.