The Effect of Acidic Residues on the Binding between Opicalcin1 and Ryanodine Receptor from the Structure-Functional Analysis.

Calcin is a group ligand with high affinity and specificity for the ryanodine receptors (RyRs). Little is known about the effect of its acidic residues on the spacial structure as well as the interaction with RyRs. We screened the opicalcin1 acidic mutants and investigated the effect of mutation on activity. The results indicated that all acidic mutants maintained the structural features, but their surface charge distribution underwent significant changes. Molecular docking and dynamics simulations were used to analyze the interaction between opicalcin1 mutants and RyRs, which demonstrated that all opicalcin1 mutants effectively bound to the channel domain of RyR1. This stable binding induced a pronounced asymmetry in the structure of the RyR tetramer, exhibiting a high degree of structural dissimilarity. [3H]Ryanodine binding to RyR1 was enhanced in D2A and D15A, which was similar to opicalcin1, but that effect was suppressed in E12A and E29A and reversed for the DE-4A, thereby inhibiting ryanodine binding. Opicalcin1 and DE-4A also exhibited the ability to form stable docking structures with RyR2. Acidic residues play a crucial role in the structure of calcin and its functional interaction with RyRs that is beneficial for the calcin optimization to develop more active peptide lead compounds for RyR-related diseases.

Effects of Different Flotation Agents on the Nucleation and Growth of Potassium Chloride.

The flotation agent is an important collector in the production of potassium chloride and is brought into the crystallization stage with the reflux of the mother liquor. Octadecylamine Hydrochloride (ODA), 1-Dodecylamine Hydrochloride (DAH) and Sodium 1-dodecanesulfonate (SDS) were selected to study their effect on the nucleation of potassium chloride. Focused Beam Reflectance Measurement was used to collect the nucleation-induced periods of KCl in the presence of flotation agents at different supersaturations. Then, empirical equations, classical nucleation theory and growth mechanism equations were employed for data analysis. It was found that the presence of flotation agents increased the nucleation sequence m, and m(ODA) > m(SDS) > m(DAH) > m(H2O). In addition, the interfacial energy data obtained using classical nucleation theory suggest that the flotation agents used in our paper promoted the homogeneous nucleation of KCl (reduced from 5.3934 mJ·m-2 to 5.1434 mJ·m-2) and inhibited the heterogeneous nucleation of KCl (increased from 2.8054 mJ·m-2 to 3.6004 mJ·m-2). This investigation also revealed that the growth of potassium chloride was consistent with the 2D nucleation-mediated growth mechanism, and the addition of flotation agent did not change the growth mechanism of potassium chloride. Finally, the particle size distribution results were exactly consistent with the order of nucleation order m. The study of nucleation kinetics and growth mechanisms of different flotation agents on potassium chloride can provide guidance for optimizing the production process of potassium chloride and developing new flotation agents.

Nitrogenase Chemistry at 10 Kelvin─Phototautomerization and Recombination of CO-Inhibited α-H195Q Enzyme.

CO-bound forms of nitrogenase are N2-reduction inhibited and likely intermediates in Fischer-Tropsch chemistry. Visible-light photolysis at 7 K was used to interrogate all three known CO-related EPR-active forms as exhibited by the α-H195Q variant of Azotobacter vinelandii nitrogenase MoFe protein. The hi(5)-CO EPR signal converted to the hi-CO EPR signal, which reverted at 10 K. FT-IR monitoring revealed an exquisitely light-sensitive "Hi-2" species with bands at 1932 and 1866 cm-1 that yielded "Hi-1" with bands at 1969 and 1692 cm-1, which reverted to "Hi-2". The similarities of photochemical behavior and recombination kinetics showed, for the first time, that hi-CO EPR and "Hi-1" IR signals arise from one chemical species. hi(5)-CO EPR and "Hi-2" IR signals are from a second species, and lo-CO EPR and "Lo-2" IR signals, formed after prolonged illumination, are from a third species. Comparing FT-IR data with CO-inhibited MoFe-protein crystal structures allowed assignment of CO-bonding geometries in these species.

Scutellarein protects against cardiac hypertrophy via suppressing TRAF2/NF-κB signaling pathway.

BACKGROUND: Scutellarein, a widely studied ingredient of scutellaria herbs, has higher bioavailability and solubility than that of scutellarin. Although the scutellarein had been reported to modulate numerous biological functions, its ability in suppressing cardiac hypertrophy remains unclear. Hence, the present study attempted to investigate whether scutellarein played critical roles in preventing phenylephrine (PE)-induced cardiac hypertrophy. METHODS AND RESULTS: Immunocytochemistry (ICC) was employed for evaluating the morphology of the treated cardiomyocytes. Real-time PCR and western blot were respectively applied to assess the mRNA levels and protein expression of the relevant molecules. Bioinformatics analyses were carried out to investigate the potential mechanisms by which scutellarein modulated the PE-induced cardiac hypertrophy. The results showed that Scutellarein treatment significantly inhibited PE-induced increase in H9c2 and AC16 cardiomyocyte size. Besides, scutellarein treatment also dramatically suppressed the expression of the cardiac hypertrophic markers: ANP, BNP and ß-MHC. Furthermore, the effects of scutellarein on attenuating the cardiac hypertrophy might be mediated by suppressing the activity of TRAF2/NF-κB signaling pathway. CONCLUSIONS: Collectively, our data indicated that scutellarein could protect against PE-induced cardiac hypertrophy via regulating TRAF2/NF-κB signaling pathway using in vitro experiments.

Insight into the Nucleation Mechanism of p-Methoxybenzoic Acid in Ethanol-Water System from Metastable Zone Width.

The metastable zone width (MSZW) of p-methoxybenzoic acid (PMBA) in an ethanol-water system was measured using the polythermal method. The nucleation order m obtained by the Nývlt's model indicates the nucleation of PMBA following a progressive nucleation mechanism at low saturation temperature (m = 3.18-7.50) and an instantaneous nucleation mechanism at high saturation temperature (m = 1.46-2.55). Then, combined with the metastable zone experiment and the Sangwal model, we found that the MSZW and the interfacial energy reached the maximum when the mass fraction of ethanol was 0.8, which resulted in the smallest crystal product size. Meanwhile, the maximum rcrit and ΔGcrit obtained based on the modified Sangwal model indicating the PMBA needs to overcome a higher nucleation barrier in the ethanol mass fraction of 0.8. Finally, we proposed a preferential strategy for adjusting MSZW by correlating the interfacial energy with the change in ethanol mass fraction, saturation temperature, and cooling rate, respectively.

The antifungal peptide CGA-N12 inhibits cell wall synthesis of Candida tropicalis by interacting with KRE9.

CGA-N12, an antifungal peptide derived from chromogranin A, has specific antagonistic activity against Candida spp., especially against Candida tropicalis, by inducing cell apoptosis. However, the effect of CGA-N12 on the Candida cell wall is unknown. The Candida protein KRE9, which possesses ß-1,6-glucanase activity, was screened by affinity chromatography after binding to CGA-N12. In this study, the effect of CGA-N12 on KRE9 and the interaction between CGA-N12 and KRE9 was studied to clarify the effect of CGA-N12 on C. tropicalis cell wall synthesis. The effect of CGA-N12 on recombinant KRE9 ß-1,6-glucanase activity was investigated by analyzing the consumption of glucose. The results showed that CGA-N12 inhibited the activity of KRE9. After C. tropicalis was treated with CGA-N12, the structure of the C. tropicalis cell wall was damaged. The interaction between CGA-N12 and KRE9 was analyzed by isothermal titration calorimetry (ITC). The results showed that their interaction process was involved an endothermic reaction, and the interaction force was mainly hydrophobic with a few electrostatic forces. The results of the fluorescence resonance energy transfer (FRET) assay showed that the distance between CGA-N12 and KRE9 was 7 ∼ 10 nm during their interaction. Therefore, we concluded that the target of CGA-N12 in the C. tropicalis cell membrane is KRE9, and that CGA-N12 weakly binds to KRE9 within a 7 ∼ 10 nm distance and inhibits KRE9 activity.

Binding Properties of DNA and Antimicrobial Peptide Chensinin-1b Containing Lipophilic Alkyl Tails.

Multidrug-resistant bacteria present an important threat to human health. In this study, due to the weak antimicrobial activity of chensinin-1b against multidrug-resistant (MDR) bacteria, three lipo-chensinin-1b peptides, including OA-C1b, LA-C1b and PA-C1b, were designed and their activities against MDR bacteria were examined. Both the OA-C1b and LA-C1b peptides exhibited potent antimicrobial activity against selected multidrug-resistant bacterial strains. In addition to the direct disruption of bacterial membranes by antimicrobial peptides, it has also been proposed that DNA is a superior intracellular target for antimicrobial peptides. ctDNA was used as a model to investigate the binding properties of DNA and lipo-chensinin-1b peptides using a variety of biophysical methods. The kinetics results of both UV-Vis and CD spectroscopy suggested that the interaction between lipo-chensinin-1b peptides and ctDNA was concentration-dependent and resulted in an increase in polynucleotide helicity. Viscosity measurements, Trp fluorescence and iodide quenching experiments indicated that nonclassical groove binding and electrostatic binding interaction modes were utilized when the peptides interacted with the ctDNA. In addition, the formation of peptide-ctDNA complexes was monitored using dynamic light scattering experiments, during which the peptide exhibited the ability to neutralize the negative charges on the surface of the ctDNA. These results promote the possibility of designing peptide-based antibiotics targeted to DNA.

Potential role of a series of lysine-/leucine-rich antimicrobial peptide in inhibiting lipopolysaccharide-induced inflammation.

Antimicrobial peptides have broad-spectrum killing activities against bacteria, enveloped viruses, fungi and several parasites via cell membrane permeation and exhibit primarily immunomodulatory and anti-infective functions in their interactions with host cells. However, the mechanism underlying their anti-inflammatory activity remains to be elucidated. L-K6, an analog of temporin-1CEb isolated from the skin secretion of Rana chensinensis, has demonstrated a wide range of antimicrobial activities against gram-negative and gram-positive bacteria. In this study, the potent anti-inflammatory mechanism of L-K6 and its analogs in lipopolysaccharide (LPS)-stimulated human macrophage U937 cells were evaluated. We found that L-K6 suppressed the expression of inflammatory factors by two downstream signaling components in the MyD88-dependent pathway, including the mitogen-activated protein kinases (MAPKs) and the NF (nuclear factor)-κB signaling pathway, but its analog L-K5, which had the same amino acid sequence as L-K6 but no Lys residue at the -COOH terminal, only inhibited the phosphorylation of I-κB and NF-κB. Importantly, L-K6 and L-K5 were actively taken up by U937 cells through an independent cell membrane disruption mechanism and were eventually localized to the perinuclear region. The L-K6 uptake process was mediated by endocytosis, but L-K5 was specifically taken up by U937 cells via TLR4 endocytosis. Our results demonstrated that L-K6 can neutralize LPS and diassociate LPS micelles to inhibit LPS from triggering the proinflammatory signaling pathway, and by partially inhibiting inflammatory responses by the intracellular target. However, L-K5 may mainly inhibit proinflammatory responses by intracellular reporters to modulate the NF-κB signaling pathway.

Keto acid metabolites of branched-chain amino acids inhibit oxidative stress-induced necrosis and attenuate myocardial ischemia-reperfusion injury.

Branched chain α-keto acids (BCKAs) are endogenous metabolites of branched-chain amino acids (BCAAs). BCAA and BCKA are significantly elevated in pathologically stressed heart and contribute to chronic pathological remodeling and dysfunction. However, their direct impact on acute cardiac injury is unknown. Here, we demonstrated that elevated BCKAs significantly attenuated ischemia-reperfusion (I/R) injury and preserved post I/R function in isolated mouse hearts. BCKAs protected cardiomyocytes from oxidative stress-induced cell death in vitro. Mechanistically, BCKA protected oxidative stress induced cell death by inhibiting necrosis without affecting apoptosis or autophagy. Furthermore, BCKAs, but not BCAAs, protected mitochondria and energy production from oxidative injury. Finally, administration of BCKAs during reperfusion was sufficient to significantly attenuate cardiac I/R injury. These findings uncover an unexpected role of BCAA metabolites in cardioprotection against acute ischemia/reperfusion injury, and demonstrate the potential use of BCKA treatment to preserve ischemic tissue during reperfusion.

Thermodynamics of the Electron Acceptors in Heliobacterium modesticaldum: An Exemplar of an Early Homodimeric Type I Photosynthetic Reaction Center.

The homodimeric type I reaction center in heliobacteria is arguably the simplest known pigment-protein complex capable of conducting (bacterio)chlorophyll-based conversion of light into chemical energy. Despite its structural simplicity, the thermodynamics of the electron transfer cofactors on the acceptor side have not been fully investigated. In this work, we measured the midpoint potential of the terminal [4Fe-4S](2+/1+) cluster (FX) in reaction centers from Heliobacterium modesticaldum. The FX cluster was titrated chemically and monitored by (i) the decrease in the level of stable P800 photobleaching by optical spectroscopy, (ii) the loss of the light-induced g ≈ 2 radical from P800(+•) following a single-turnover flash, (iii) the increase in the low-field resonance at 140 mT attributed to the S = (3)/2 ground spin state of FX(-), and (iv) the loss of the spin-correlated P800(+) FX(-) radical pair following a single-turnover flash. These four techniques led to similar estimations of the midpoint potential for FX of -502 ± 3 mV (n = 0.99), -496 ± 2 mV (n = 0.99), -517 ± 10 mV (n = 0.65), and -501 ± 4 mV (n = 0.84), respectively, with a consensus value of -504 ± 10 mV (converging to n = 1). Under conditions in which FX is reduced, the long-lived (∼15 ms) P800(+) FX(-) state is replaced by a rapidly recombining (∼15 ns) P800(+)A0(-) state, as shown by ultrafast optical experiments. There was no evidence of the presence of a P800(+) A1(-) spin-correlated radical pair by electron paramagnetic resonance (EPR) under these conditions. The midpoint potentials of the two [4Fe-4S](2+/1+) clusters in the low-molecular mass ferredoxins were found to be -480 ± 11 mV/-524 ± 13 mV for PshBI, -453 ± 6 mV/-527 ± 6 mV for PshBII, and -452 ± 5 mV/-533 ± 8 mV for HM1_2505 as determined by EPR spectroscopy. FX is therefore suitably poised to reduce one [4Fe-4S](2+/1+) cluster in these mobile electron carriers. Using the measured midpoint potential of FX and a quasi-equilibrium model of charge recombination, the midpoint potential of A0 was estimated to be -854 mV at room temperature. The midpoint potentials of A0 and FX are therefore 150-200 mV less reducing than their respective counterparts in Photosystem I of cyanobacteria and plants. This places the redox potential of the FX cluster in heliobacteria approximately equipotential to the highest-potential iron-sulfur cluster (FA) in Photosystem I, consistent with its assignment as the terminal electron acceptor.

Interactions between chensinin-1, a natural antimicrobial peptide derived from Rana chensinensis, and lipopolysaccharide.

Lipopolysaccharide (LPS) plays a critical role in the pathogenesis of sepsis caused by gram-negative bacterial infections. Therefore, LPS-neutralizing molecules would have important clinical applications. Chensinin-1, a novel antimicrobial peptide with atypical structural features, was found in the skin secretions of the Chinese brown frog Rana chensinensis. To understand the role of LPS in the bacterial susceptibility to chensinin-1 and to investigate its anti-endotoxin effects, the interactions of chensinin-1 with LPS were investigated in this study using circular dichroism, in situ IR, isothermal titration calorimetry, and zeta potential. This study is the first to use in situ IR spectroscopy to evaluate the secondary structural changes of this peptide. The capacity of chensinin-1 to block the LPS-dependent cytokine secretion of macrophages was also investigated. Our results show that chensinin-1 can form α-helical structures in LPS suspensions. LPS can affect the antimicrobial activity of chensinin-1, and chensinin-1 was able to mitigate the effects of LPS. These data may facilitate the development of antimicrobial peptides with potent antimicrobial and anti-endotoxin activities.

[Study on binding forms of selenium in selenium-enriched Salvia miltiorrhiza].

OBJECTIVE: To understand the absolute and relative concentrations of proteins,polysaccharides and nucleic acids that are Selenium-binding in Selenium-enriched Salvia miltiorrhiza, and to determine the efficiency of biotransformation of inorganic Selenium compounds in Salvia miltiorrhiza. METHODS: Extract the Selenium-binding proteins, polysaccharides and nucleic acids in Selenium-enriched Salvia miltiorrhiza using different solvents. Determine the concentrations of proteins, polysaccharides and nucleic acids by spectrophotometry, the concentration of Selenium by Hydride generation atomic fluorescence spectrometry. RESULTS: Selenium-binding proteins took up 74.2% of the total amount of Selenium in the tested Salvia miltiorrhiza, while Selenium-binding polysaccharides took up 39.5% and Selenium-binding nucleic acids took up 2.3%. Selenium that was bound with the water-soluble proteins came out as the most con- centrated, taking up 46.0% of the total amount of Selenium, during the extraction of Selenium using water, NaCl, ethanol and NaOH solution, respectively. Being extracted by the weak acid and alkali phosphoric acid buffer solutions, Selenium-binding proteins were more concentrated in the alkali buffer solution, taking up 51.2% of the total amount. CONCLUSIONS: In Salvia miltiorrhiza, Selenium exists mainly in the forms of selenium-binding proteins and Selenium-binding polysaccharides. Cultivation of Selenium-enriched Salvia miltiorrhiza achieves the biotransformation of inorganic Selenium compounds into organic compounds efficiently.

Quantitative analysis of low-content impurity crystal forms in canagliflozin tablets by NIR solid-state analysis technique.

Canagliflozin (CFZ) tablets was a commercially new class of anti-diabetic drug, CFZ had various anhydrate crystal forms and two hydrate crystal forms (Canagliflozin hemihydrate (Hemi-CFZ) and Canagliflozin monohydrate (Mono-CFZ) crystal form). The active pharmaceutical ingredients (APIs) of commercially available CFZ tablets were Hemi-CFZ, was easily convert to CFZ or Mono-CFZ under the influence of temperature, pressure, humidity and other factors in tablets processing, storage, and transportation, thus affected bioavailability and efficacy of tablets. Therefore, quantitative analysis of low-content CFZ and Mono-CFZ in tablets was essential to control tablets' quality. The main objective of this study was to explore the feasibility and in-depth explain its quantitative analysis mechanism of NIR for quantitative analysis of low-content CFZ/Mono-CFZ in CFZ tablets. PLSR models for low-content CFZ/Mono-CFZ were established by NIR solid-state analysis technique in different resolutions with different wavenumber regions combined with various pretreatments methods (such as Multiplicative Scatter Correction (MSC), Standard Normal Variate (SNV), Savitzky-Golay First Derivative (SG1st), Savitzky-Golay Second Derivative (SG2nd) and Wavelet Transform (WT)), and the PLSR models were verified. The feasibility of NIR spectroscopy for quantitative analysis of low-content CFZ and Mono-CFZ in CFZ tablets was discussed and analyzed from multiple perspectives, which included the distribution of effective information on the spectrum, the influence of resolution on PLSR models performance, the variance contribution/cumulative variance contribution of PLSR model principal components (PCs), the relation of PCI loadings, scores of the spectra and CFZ/Mono-CFZ content, and the mechanism of quantitative analysis was in-depth explained simultaneously. Eventually the most suitable PLSR models in 0.0000-10.0000 % w/w % obtained. That can provide theoretical support for quantitative analysis of low-content impurity crystal during the production, storage and transportation of CFZ tablets, thus provide reference methods for quality control of CFZ tablets and a reliable reference method for quantitative analysis of impurity crystal forms and quality control of similar drugs.

Energy calibration issues in nuclear resonant vibrational spectroscopy: observing small spectral shifts and making fast calibrations.

The conventional energy calibration for nuclear resonant vibrational spectroscopy (NRVS) is usually long. Meanwhile, taking NRVS samples out of the cryostat increases the chance of sample damage, which makes it impossible to carry out an energy calibration during one NRVS measurement. In this study, by manipulating the 14.4 keV beam through the main measurement chamber without moving out the NRVS sample, two alternative calibration procedures have been proposed and established: (i) an in situ calibration procedure, which measures the main NRVS sample at stage A and the calibration sample at stage B simultaneously, and calibrates the energies for observing extremely small spectral shifts; for example, the 0.3 meV energy shift between the 100%-(57)Fe-enriched [Fe4S4Cl4](=) and 10%-(57)Fe and 90%-(54)Fe labeled [Fe4S4Cl4](=) has been well resolved; (ii) a quick-switching energy calibration procedure, which reduces each calibration time from 3-4 h to about 30 min. Although the quick-switching calibration is not in situ, it is suitable for normal NRVS measurements.

Inelastic X-ray scattering of a transition-metal complex (FeCl4(-)): vibrational spectroscopy for all normal modes.

The tetraethylammonium salt of the transition-metal complex FeCl4(-) has been examined using inelastic X-ray scattering (IXS) with 1.5 meV resolution (12 cm(-1)) at 21.747 keV. This sample serves as a feasibility test for more elaborate transition-metal complexes. The IXS spectra were compared with previously recorded IR, Raman, and nuclear resonant vibrational spectroscopy (NRVS) spectra, revealing the same normal modes but with less strict selection rules. Calculations with a previously derived Urey-Bradley force field were used to simulate the expected Q and orientation dependence of the IXS intensities. The relative merits of IXS, compared to other photon-based vibrational spectroscopies such as NRVS, Raman, and IR, are discussed.

Membrane-active and DNA binding related double-action antimycobacterial mechanism of antimicrobial peptide W3R6 and its synthetic analogs.

The emergence of multidrug- or extremely drug-resistant M. tuberculosis strains has made very few drugs available for current tuberculosis treatment. Antimicrobial peptides can be employed as a promising alternative strategy for TB treatment. Here, we designed and synthesized a series of peptide sequences based on the structure-activity relationships of natural sequences of antimicrobial peptides. The peptide W3R6 and its analogs were screened and found to have potent antimycobacterial activity against M. smegmatis, and no hemolytic activity against human erythrocytes. The evidence from the mechanism of action study indicated that W3R6 and its analogs can interact with the mycobacterial membrane in a lytic manner and form pores on the outer membrane of M. smegmatis. Significant colocalization of D-W3R6 with mycobacterial DNA was observed by confocal laser scanning microscopy and DNA retardation assays, which suggested that the antimycobacterial mechanism of action of the peptide was associated with the unprotected genomic DNA of M. smegmatis. In general, W3R6 and its analogs act on not only the mycobacterial membrane but also the genomic DNA in the cytoplasm, which makes it difficult for mycobacteria to generate resistance due to the peptides having two targets. In addition, the peptides can effectively eliminate M. smegmatis cells from infected macrophages. Our findings indicated that the antimicrobial peptide W3R6 could be a novel lead compound to overcome the threat from drug-resistant M. tuberculosis strains in the development of potent AMPs for TB therapeutic applications.

Significance of NotchScore and JAG1 in predicting prognosis and immune response of low-grade glioma.

Introduction: Low-grade glioma (LGG) is a prevalent malignant tumor in the intracranial region. Despite the advancements in treatment methods for this malignancy over the past decade, significant challenges still persist in the form of drug resistance and tumor recurrence. The Notch signaling pathway plays essential roles in many physiological processes as well as in cancer development. However, the significance of the pathway and family genes in LGG are poorly understood. Methods: We conducted gene expression profiling analysis using the TCGA dataset to investigate the gene set associated with the Notch signaling pathway. we have proposed a metric called "NotchScore" that quantifies the strength of the Notch signaling pathway and enables us to assess its significance in predicting prognosis and immune response in LGG. We downregulated JAG1 in low-grade gliomas to assess its influence on the proliferation and migration of these tumors. Ultimately, we determined the impact of the transcription factor VDR on the transcription of PDL1 through chip-seq data analysis. Results: Our findings indicate that tumors with a higher NotchScore, exhibit poorer prognosis, potentially due to their ability to evade the anti-tumor effects of immune cells by expressing immune checkpoints. Among the genes involved in the Notch signaling pathway, JAG1 has emerged as the most representative in terms of capturing the characteristics of both NotchScore and Notch pathways. The experimental results demonstrate that silencing JAG1 yielded a significant decrease in tumor cell proliferation in LGG cell lines. Our study revealed mechanisms by which tumors evade the immune system through the modulation of PDL1 transcription levels via the PI3K-Akt signaling pathway. Additionally, JAG1 potentially influences PDL1 in LGG by regulating the PI3K-Akt signaling pathway and the expression of the transcription factor VDR. Discussion: These findings contribute to our understanding of immune evasion by tumors in LGG. The insights gained from this research may have implications for the development of therapeutic interventions for LGG.

Effect of hydrophobicity on distinct anticancer mechanism of antimicrobial peptide chensinin-1b and its lipoanalog PA-C1b in breast cancer cells.

Chensinin-1b and its lipoanalogs demonstrate different anticancer activities against selected cancer cells, and the anticancer activity of PA-C1b is improved up to 3-fold compared with that of the parent peptide chensinin-1b. However, detailing the mechanism of action of these peptides is required to better understand the structure-function relationship. In this study, chensinin-1b and PA-C1b were selected as the representative peptides to investigate the mode of action in cancer cells. The results indicated that the boundary of the cell membrane was broken when the cells were treated with chensinin-1b, while that of cells treated with PA-C1b remained intact based on morphological changes. Apoptosis assays indicated that PA-C1b induced MCF-7 cancer cell apoptosis, while chensinin-1b mainly damaged the cell membrane. MCF-7 cancer cells treated with the peptides induced the loss of mitochondrial membrane potential, and cytochrome c was released from mitochondria, but PA-C1b enhanced ROS generation. Additionally, PA-C1b uptake occurred via an energy-dependent pathway and was inhibited by selected endocytosis inhibitors. Furthermore, treatment of MCF-7 cells with PA-C1b suppressed Bcl-2 mRNA levels and increased Bax mRNA levels, upregulated the expression of the proapoptotic protein Bax and downregulated the expression of the antiapoptotic protein Bcl-2. These results indicate that the anticancer mechanism of AMPs may be considerably affected by only a slight difference in the hydrophobicity of the two peptides; and such a study may facilitate the design of novel peptide-based anticancer agents.

TCNQ-based organic cocrystal integrated red emission and n-type charge transport.

Simultaneously realizing the optical and electrical properties of organic materials is always challenging. Herein, a convenient and promising strategy for designing organic materials with integrated optoelectronic properties based on cocrystal engineering has been put forward. By selecting the fluorene (Flu) and the 7,7',8,8'-tetracyanoquinodimethane (TCNQ) as functional constituents, the Flu-TCNQ cocrystal prepared shows deep red emission at 702 nm, which is comparable to the commercialized red quantum dot. The highest electron mobility of organic field-effect transistor (OFET) based on Flu-TCNQ is 0.32 cm2 V-1 s-1. Spectroscopic analysis indicates that the intermolecular driving force contributing to the co-assembly of Flu-TCNQ is mainly charge transfer (CT) interaction, which leads to its different optoelectronic properties from constituents.

Dynamics of the [4Fe-4S] cluster in Pyrococcus furiosus D14C ferredoxin via nuclear resonance vibrational and resonance Raman spectroscopies, force field simulations, and density functional theory calculations.

We have used (57)Fe nuclear resonance vibrational spectroscopy (NRVS) to study oxidized and reduced forms of the [4Fe-4S] cluster in the D14C variant ferredoxin from Pyrococcus furiosus (Pf D14C Fd). To assist the normal-mode assignments, we conducted NRVS with D14C ferredoxin samples with (36)S substituted into the [4Fe-4S] cluster bridging sulfide positions, and a model compound without ligand side chains, (Ph(4)P)(2)[Fe(4)S(4)Cl(4)]. Several distinct regions of NRVS intensity are identified, ranging from "protein" and torsional modes below 100 cm(-1), through bending and breathing modes near 150 cm(-1), to strong bands from Fe-S stretching modes between 250 and ∼400 cm(-1). The oxidized ferredoxin samples were also investigated by resonance Raman (RR) spectroscopy. We found good agreement between NRVS and RR frequencies, but because of different selection rules, the intensities vary dramatically between the two types of spectra. The (57)Fe partial vibrational densities of states for the oxidized samples were interpreted by normal-mode analysis with optimization of Urey-Bradley force fields for local models of the [4Fe-4S] clusters. Full protein model calculations were also conducted using a supplemented CHARMM force field, and these calculations revealed low-frequency modes that may be relevant to electron transfer with Pf Fd partners. Density functional theory (DFT) calculations complemented these empirical analyses, and DFT was used to estimate the reorganization energy associated with the [Fe(4)S(4)](2+/+) redox cycle. Overall, the NRVS technique demonstrates great promise for the observation and quantitative interpretation of the dynamical properties of Fe-S proteins.