Development of a Smart Fluorescent Probe Specifically Interacting with C-Myc I-Motif.

I-motifs play key regulatory roles in biological processes, holding great potential as attractive therapeutic targets. In the present study, we developed a novel fluorescent probe G59 with strong and selective binding to the c-myc gene promoter i-motif. G59 had an i-motif-binding carbazole moiety conjugated with naphthalimide fluorescent groups. G59 could differentiate the c-myc i-motif from other DNA structures through selective activation of its fluorescence, with its apparent visualization in solution. The smart probe G59 showed excellent sensitivity, with a low fluorescent detection limit of 154 nM and effective stabilization to the c-myc i-motif. G59 could serve as a rapid and sensitive probe for label-free screening of selective c-myc i-motif binding ligands under neutral crowding conditions. To the best of our knowledge, G59 is the first fluorescent probe with high sensitivity for recognizing the i-motif structure and screening for selective binding ligands.

Transcriptional regulation of telomeric repeat-containing RNA by acridine derivatives.

Telomere is a specialized DNA-protein complex that plays an important role in maintaining chromosomal integrity. Shelterin is a protein complex formed by six different proteins, with telomeric repeat factors 1 (TRF1) and 2 (TRF2) binding to double-strand telomeric DNA. Telomeric DNA consists of complementary G-rich and C-rich repeats, which could form G-quadruplex and intercalated motif (i-motif), respectively, during cell cycle. Its G-rich transcription product, telomeric repeat-containing RNA (TERRA), is essential for telomere stability and heterochromatin formation. After extensive screening, we found that acridine derivative 2c and acridine dimer DI26 could selectively interact with TRF1 and telomeric i-motif, respectively. Compound 2c blocked the binding of TRF1 with telomeric duplex DNA, resulting in up-regulation of TERRA. Accumulated TERRA could bind with TRF1 at its allosteric site and further destabilize its binding with telomeric DNA. In contrast, DI26 could destabilize telomeric i-motif, resulting in down-regulation of TERRA. Both compounds exhibited anti-tumour activity for A549 cells, but induced different DNA damage pathways. Compound 2c significantly suppressed tumour growth in A549 xenograft mouse model. The function of telomeric i-motif structure was first studied with a selective binding ligand, which could play an important role in regulating TERRA transcription. Our results showed that appropriate level of TERRA transcript could be important for stability of telomere, and acridine derivatives could be further developed as anti-cancer agents targeting telomere. This research increased understanding for biological roles of telomeric i-motif, TRF1 and TERRA, as potential anti-cancer drug targets.

Syntheses and evaluation of acridone-naphthalimide derivatives for regulating oncogene PDGFR-ß expression.

Upregulation of platelet-derived growth factor receptor ß (PDGFR-ß) has been found to be associated with development of various types of cancers, which has become an attractive target for anti-tumor treatment. Previously, we have synthesized and studied an acridone derivative B19, which can selectively bind to and stabilize oncogene c-myc promoter i-motif, resulting in down-regulation of c-myc transcription and translation, however its effect on tumor cells apoptosis requires improvement. In the present study, we synthesized a variety of B19 derivatives containing a known anti-cancer fluorescent chromophore naphthalimide for the purpose of enhancing anti-cancer activity. After screening, we found that acridone-naphthalimide derivative WZZ02 could selectively stabilize PDGFR-ß promoter G-quadruplex and destabilize its corresponding i-motif structure, without significant interaction to other oncogenes promoter G-quadruplex and i-motif. WZZ02 down-regulated PDGFR-ß gene transcription and translation in a dose-dependent manner, possibly due to above interactions. WZZ02 could significantly inhibit cancer cell proliferation, and induce cell apoptosis and cycle arrest. WZZ02 exhibited tumor growth inhibition activity in MCF-7 xenograft tumor model, which could be due to its binding interactions with PDGFR-ß promoter G-quadruplex and i-motif. Our results suggested that WZZ02 as a dual G-quadruplex/i-motif binder could be effective on both oncogene replication and transcription, which could become a promising lead compound for further development with improved potency and selectivity. The wide properties for the derivatives of 1,8-naphthalimide could facilitate further in-depth mechanistic studies of WZZ02 through various fluorescent physical and chemical methods, which could help to further understand the function of PDGFR-ß gene promoter G-quadruplex and i-motif.

Position Effect of Fatty Acid Modification on the Cytotoxicity and Antimetastasis Potential of the Cytotoxic Peptide Lycosin-I.

Peptide modification with fatty acids is an effective method to improve peptide performance. We previously investigated the fatty acid modification of R-lycosin-I, a cytotoxic peptide derived from lycosin-I from the venom of the spider Lycosa singoriensis. In this study, we further investigated the position effects of fatty acid modification of lycosin-I. Dodecanoic acid was covalently coupled to the α/ε-amino group of one of the seven Lys residues of lycosin-I, generating eight different lipopeptides. Although all the lipopeptides had significantly improved cytotoxicity compared with lycosin-I, they displayed different cytotoxic potencies and profiles, which might be explained by multifactors including charge, size, helicity, hydrophobicity, and so forth. Of the eight lipopeptides, L-C12 demonstrated highest cytotoxicity and antimetastasis activity in two-dimensional cells, tumor spheroids, subcutaneous transplantation mouse models, and experimental melanoma metastasis mouse models. Collectively, our finding indicated that fatty acid modification position plays important roles in physiochemical parameters and biological activities of cytotoxic peptides.

Monosaccharide Analogues of Anticancer Peptide R-Lycosin-I: Role of Monosaccharide Conjugation in Complexation and the Potential of Lung Cancer Targeting and Therapy.

Glycoconjugation is a promising modification strategy for the optimization of peptide drugs. In this study, five different monosaccharide derivatives (7a-e) were covalently linked to the N-terminal of R-lycosin-I, which yielded five glycopeptides (8a-e). They demonstrated increased or reduced cytotoxicity depending on monosaccharide types, which might be explained by the changes of physicochemical properties. Among all synthesized glycopeptides, only 8a exhibited increased cytotoxicity (IC50 = 9.6 ± 0.3 µM) and selectivity (IC50 = 37.4 ± 5.9 µM). The glucose transporter 1 (GLUT1) with high expression in cancer cells was approved to be involved in the cytotoxicity and selectivity enhancement of 8a. Furthermore, 8a but not R-lycosin-I inhibited tumor growth in the nude mice xenograft model without generating side effects intraperitoneally. Taken together, this study reveals the different monosaccharide roles in peptide modification and also provides an optimized anticancer peptide with high activity and selectivity, that is, 8a might be a promising lead for developing anticancer drugs.

Biosafety Level 4 Laboratory User Training Program, China.

Experienced, qualified personnel certified to work in high-level biocontainment laboratories contribute to the safe operation of these facilities. China began a training program for laboratory users after establishing its first Biosafety Level 4 laboratory, the Wuhan National Biosafety Laboratory (Level 4) of the Chinese Academy of Sciences. We provide an overview of the content of this training program, which can serve as a reference for developing national norms for high-containment laboratory training.

The Roles of Fatty-Acid Modification in the Activity of the Anticancer Peptide R-Lycosin-I.

We previously reported that R-lycosin-I, modified by amino acid substitution from lycosin-I, was a peptide with anticancer activity and a linear amphipathic α-helix conformation and that it can induce cancer cell apoptosis and inhibit cell proliferation. However, the anticancer activity of R-lycosin-I was not highly improved. In order to further improve the anticancer activity of R-lycosin-I, fatty acids with different chain lengths from 12 to 20 carbons were introduced to the N-terminal of R-lycosin-I to yield five lipopeptides (R-C12, R-C14, R-C16, R-C18, R-C20). The physicochemical properties of the five lipopeptides were determined by hydrodynamic size, ζ-potential, and circular dichroism spectroscopy, respectively. Then, the cytotoxic activity of these lipopeptides in A549 cells was evaluated with serum-containing and serum-free media, respectively, showing their anticancer activities were all increased through fatty-acid modification. This may be a result of the increased hydrophobicity and the enhanced interaction with the cancer cell membrane. The cytotoxic activity of R-C16 was 3-4-fold higher than that of the original R-lycosin-I and also was the strongest among all five lipopeptides, whether in serum or serum-free conditions. Compared with R-lycosin-I, the lactate dehydrogenase (LDH) leakage assay and scanning electron microscopy (SEM) indicated that R-C16 had a weakly destructive effect on the cancer cell membrane, but it might cause apoptosis to exert an anticancer activity. Finally, the impacts of fatty-acid length on the physicochemical properties and the anticancer potential of peptide were discussed. Our data consolidate work on fatty-acid-modified anticancer peptides.

Open Resonator Electric Spaser.

The inception of the plasmonic laser or spaser (surface plasmon amplification by stimulated emission of radiation) concept in 2003 provides a solution for overcoming the diffraction limit of electromagnetic waves in miniaturization of traditional lasers into the nanoscale. From then on, many spaser designs have been proposed. However, all existing designs use closed resonators. In this work, we use cavity quantum electrodynamics analysis to theoretically demonstrate that it is possible to design an electric spaser with an open resonator or a closed resonator with much weak feedback in the extreme quantum limit in an all-carbon platform. A carbon nanotube quantum dot plays the role of a gain element, and Coulomb blockade is observed. Graphene nanoribbons are used as the resonator, and surface plasmon polariton field distribution with quantum electrodynamics features can be observed. From an engineering perspective, our work makes preparations for integrating spasers into nanocircuits and/or photodynamic therapy applications.

Arginine modification of lycosin-I to improve inhibitory activity against cancer cells.

Lycosin-I is a linear amphipathic α-helical anticancer peptide (ACP) extracted from the spider Lycosa singoriensis, which can activate the mitochondrial death pathway to induce apoptosis in tumor cells and up-regulate p27 to inhibit cell proliferation. However, the applicability of lycosin-I as a novel anticancer drug is limited by its low cellular entry and efficacy in solid tumors. Amino acid substitution presents an effective and modest strategy to improve the anticancer activity and bioavailability of ACPs. Herein, an arginine-modified lycosin-I (named R-lycosin-I) was designed and synthesized by substituting lysine (Lys) with arginine (Arg). This peptide exhibited higher anticancer activity and penetrability against solid tumor cells than lycosin-I. They displayed noticeable differences in their physicochemical properties including the secondary structure, hydrodynamic size, and zeta potential. Fluorescence analyses have confirmed that R-lycosin-I exhibits increased cellular uptake and improved intracellular distribution. Due to its superior physical and chemical properties and high serum stability, R-lycosin-I could penetrate deeply into tumor spheroids and produce strong toxicity in the 3D tumor model. Overall, these findings suggest that arginine modification may provide an effective strategy for improving the anticancer activity of lycosin-I, and R-lycosin-I may be a useful lead for developing anticancer drugs.

Conductance fluctuations in graphene in the presence of long-range disorder.

The fluctuations in the conductance of graphene that arise from a long-range disorder potential induced by random impurities are investigated with an atomic tight-binding lattice. The screened impurities lead to a slow variation of the background potential and this varies the overall potential landscape as the Fermi energy or an applied magnetic field is varied. As a result, the phase interference varies randomly and leads to fluctuations in the conductance. Recently, experiments have shown that an applied magnetic field produces a remarkable reduction in the amplitude of these conductance fluctuations. We find qualitative agreement with these experiments, and it appears that the reduction in magnetic field of the fluctuations arises from a field induced smoothing of the conductance landscape.

Conductance fluctuations in semiconductor nanostructures.

Conductance fluctuations have been seen in semiconductors and graphene for quite some time. It has generally been believed that a universality existed in which the conductance variance was the same for variations in energy and magnetic field, although some experiments have questioned this view. Here, we use numerical simulations to show that fluctuations in magneto-conductance are typically smaller than those in energy by as much as a factor of 3. Moreover, the amplitude of the fluctuations in each case varies with the strength of the random potential.