Exploring mitochondrial targeting: an innovative fluorescent probe reveals Nernstian potential and partitioning combination

This study introduces a paradigm-shifting approach to optimize mitochondrial targeting. Employing a new fluorescent probe strategy, we unravel a combined influence of both Nernst potential (Ψ) and partitioning (P) contributions. Through the synthesis of new benz[e]indolinium-derived probes, our findings redefine the landscape of mitochondrial localization by optimizing the efficacy of mitochondrial probe retention in primary cortical neurons undergoing normoxia and oxygen-glucose deprivation. This methodology not only advances our understanding of subcellular dynamics, but also holds promise for transformative applications in biomedical research and therapeutic development.

Exploring the self-assembly dynamics of novel steroid-coumarin conjugates: a comprehensive spectroscopic and solid-state investigation

The design, synthesis, and characterization of seven novel steroid-coumarin conjugates with diverse steroidal nuclei as lipophilic fluorescent materials for bioimaging applications are presented. The conjugates were synthesized through amidation, characterized using spectroscopic and spectrometric methods, and their main photophysical properties were determined. Dioxane : water titration experiments revealed their ability to self-assemble, forming J-aggregates as evidenced by new spectral bands at higher wavelengths. Monocrystal X-ray diffraction analysis disclosed distinctive aggregation patterns exhibiting J- or H-aggregates for selected compounds. Bioimaging studies demonstrated cell membrane localization for most conjugates, with some of them displaying an interesting selectivity for lipid droplets. Notably, the presence of the steroid fragments significantly influenced both the self-assembly patterns and the cellular localization of the fluorescent probes.

Fluorescent Probe for in Vivo Partitioning into Dynamic Lipid Droplets Enables Monitoring of Water Permeability-Induced Edema

Lipid droplets (LDs) are intracellular organelles found in most cell types from adipocytes to cancer cells. Although recent investigations have implicated LDs in numerous diseases, the current available methods to monitor them in vertebrate models rely on static imaging using fluorescent dyes, limiting the investigation of their rapid in vivo dynamics. Here, we report a fluorophore chemistry approach to enable in vivo LD dynamic monitoring using a Nernstian partitioning mechanism. Interestingly, the effect of atorvastatin and osmotic treatments toward LDs revealed an unprecedented dynamic enhancement. Then, using a designed molecular probe with an optimized response to hydration and LD dynamics applied to Zebrafish developing pericardial and yolk-sac edema, which represents a tractable model of a human cardiovascular disease, we also provide a unique dual method to detect disease evolution and recovery.

Mitochondria-Assisted Photooxidation to Track Singlet Oxygen at Homeostatic Membrane Microviscosity

Using intracellular-controlled photochemistry to track dynamic organelle processes is gaining attention due to its broad applications. However, most of the employed molecular probes usually require toxic photosensitizers and complex bioanalytical protocols. Here, the synthesis and performance of two new subcellular probes (MitoT1 and MitoT2) are described. The probes undergo photooxidation in the damaged tissue of zebrafish, a model system for tissue regeneration studies. Using high-resolution confocal microscopy and fluorescence spectroscopy, we combine the mentioned photoinduced interconversion at the homeostatic membrane viscosity to track singlet oxygen activity selectively. The continuous and real-time biosensing method reported here provides a new approach for simultaneously detecting endogenous singlet oxygen and viscosity status.

Fluorescent probe for early mitochondrial voltage dynamics

Mitochondrial voltage dynamics plays a crucial role in cell healthy and disease. Here, a new fluorescent probe to monitor mitochondrial early voltage variations is described. The slowly permeant probe is retained in mitochondria during measurements to avoid interferences from natural membrane potential by incorporating an hydrolizable ester function. Voltage, local polarity, pH parameters and transmembrane dynamics were found to be deeply correlated opening a approach in mitochondrial sensing.

Diversity-Oriented Synthesis of Highly Fluorescent Fused Isoquinolines for Specific Subcellular Localization

A multicomponent diversity-oriented synthesis of new highly emissive tetracyclic isoquinolines that target specific organelles is described. The title compounds were prepared via a three-step protocol starting with an Ugi four-component reaction, followed by either an intramolecular alkyne hydroarylation and subsequent alkene isomerization or through a Pomeranz-Fritsch-type cyclization with a final intramolecular Heck reaction. Subcellular localization studies of these compounds using green channel confocal microscopy revealed remarkable and distinctive distribution patterns in live cells, showing an unprecedented high selectivity and imaging contrast. The differentiated organelle visualization-including localizers for mitochondria, lysosomes, Golgi apparatus, endoplasmic reticulum, and plasma membrane-was achieved by varying the nature of the tetracyclic system and substituent pattern, changing the original four-component set in the starting Ugi reaction.

Unravelling the modus-operandi of chromenylium-cyanine fluorescent probes: a case study

Small-molecule fluorescent probes having optimized optical properties, such as high photostability and brightness, local microenvironment sensitivity and specific subcellular localizations, are increasingly available. Although the basis for designing efficient fluorophores for bioimaging applications is well established, implementing an improvement in a given photophysical characteristic always tends to compromise another optical property. This problem has enormous consequences for in vivo imaging, where ensuring a specific localization and precise control of the probe response is challenging. Herein we discuss a fluorescent probe, CC334, as a case study of the chromenylium-cyanine family that commonly exhibits highly complex photophysical schemes and highly interfered bioanalytical responses. By an exhaustive and concise analysis of the CC334 optical responses including detailed spectroscopic calibrations, steady-state microenvironment effects, ultrafast photophysics analysis and computational studies, we elucidate a new strategy to apply the probe in the singlet oxygen reactive oxygen species (1O2-ROS) monitoring using in vitro and in vivo models. The probe provides a new avenue for designing fluorescent probes to understand the dynamic behavior of subcellular environments.

Organotin(iv) differential fluorescent probe for controlled subcellular localization and nuclear microviscosity monitoring

A dual-emissive fluorescent probe based on the organotin(iv) ion enabled unique tracking of the local microviscosity through a differential and controlled nuclear–cytosolic redistribution.

A Multifunctional Chemical Probe for the Measurement of Local Micropolarity and Microviscosity in Mitochondria

The measurement of physicochemical parameters in living cells can provide information on individual cellular organelles, helping us to understand subcellular function in health and disease. While organelle-specific chemical probes have allowed qualitative evaluation of microenvironmental variations, the simultaneous quantification of mitochondrial local microviscosity (η_m ) and micropolarity (ϵ_m ), along with concurrent structural variations, has remained an unmet need. Herein, we describe a new multifunctional mitochondrial probe (MMP) for simultaneous monitoring of η_m and ϵ_m by fluorescence lifetime and emission intensity recordings, respectively. The MMP enables highly precise measurements of η_m and ϵ_m in the presence of a variety of agents perturbing cellular function, and the observed changes can also be correlated with alterations in mitochondrial network morphology and motility. This strategy represents a promising tool for the analysis of subtle changes in organellar structure.

Tracking mitochondrial 1O2-ROS production through a differential mitochondria-nucleoli fluorescent probe

A dual-emissive fluorescent probe enabled unique tracking of ¹O₂-ROS species through a differential mitochondrial–nucleoli localization dynamic.

Variation of the Molecular Conformation, Shape, and Cavity Size in Dinuclear Metalla-Macrocycles Containing Hetero-Ditopic Dithiocarbamate-Carboxylate Ligands from a Homologous Series of N-Substituted Amino Acids

A homologous series of dithiocarbamate ligands derived from N-substituted amino acids was reacted with different diorganotin dichlorides to give 18 diorganotin complexes. Spectroscopic and mass spectrometric analysis evidenced the formation of assemblies with six-coordinate tin atoms embedded in skewed-trapezoidal bipyramidal coordination environments of composition C₂SnS₂O₂. Single-crystal X-ray diffraction analysis for three of the compounds revealed a one-dimensional polymeric structure for the complex with the ligand derived from 5-aminopentanoic acid, which through further intermolecular Sn···O interactions generated an overall two-dimensional coordination polymer containing 40-membered hexanuclear tin macrocycles. On the contrary, the ligands derived from 6-aminohexanoic and 8-aminooctanoic acid provided the expected 22- and 26-membered dinuclear macrocyclic structures. Density functional theory calculations for a representative series of macrocyclic complexes of composition [Me₂SnLx]₂ with Lx = ¯S₂CN(Me)-(CH₂)_x-COO¯ (x = 3-12) enabled a detailed analysis of the variations in the molecular conformation, shape, and cavity size of the macrocycles in dependence of the aliphatic spacer. Because of odd-even effects, the difunctional ligands can adopt either a curved or a twisted-pincer shape, while the SnS_xO_4-x (x = 0-4) moieties can act either as linear or angular tectons with varying connectivity angles.

Strong Dipolar Effects on an Octupolar Luminiscent Chromophore: Implications on their Linear and Nonlinear Optical Properties

Design parameters derived from structure-property relationships play a very important role in the development of efficient molecular-based functional materials with optical properties. Here, we report on the linear and nonlinear optical properties of a fluorene-derived dipolar system (DS) and its octupolar analogue (OS), in which donor and acceptor groups are connected by a phenylacetylene linkage, as a strategy to increase the number of delocalized electrons in the π-conjugated system. The optical nonlinear response was analyzed in detail by experimental and theoretical methods, showing that, in the octupolar system OS, the dipolar effects induced a strong two-photon absorption process whose magnitude is as large as 2210 GM at infrared wavelengths. Solvatochromism studies were implemented to obtain further insight on the charge transfer process. We found that the triple bond plays a fundamental role in the linear and nonlinear optical responses. The strong solvatochromism behavior in DS and OS was analyzed by using four empirical solvent scales, namely Lippert-Mataga, Kamlet-Taft, Catalán, and the recently proposed scale of Laurence et al., finding consistent results of strong solvent polarizability and viscosity dependence. Finally, the role of the acceptor groups was further studied by synthesizing the analogous compound 2DS, having no acceptor group.

A photochromic-acidochromic HCl fluorescent probe. An unexpected chloride-directed recognition

Non-classical protomerism of Schiff bases offers several advantages; for example, specific interactions in the -C[double bond, length as m-dash]N- linkage can be controlled and differentiated because the interactions are not governed by keto-enol tautomerism. Herein, the pH sensing properties of a new protomeric Schiff base probe () are reported. In particular, among several acids, the probe displays significant optical responses upon interaction with hydrochloric acid (HCl). X-ray structural analysis confirmed the existence of an intermolecular interaction with HCl through a -C[double bond, length as m-dash]NH-ClO- linkage. Moreover, an optical response via a second channel is manifested as photochromic fluorescence behavior. The properties of were investigated by UV-vis and fluorescence spectroscopy in a solution and the solid state. Its strong acidofluorochromic behavior was analyzed and its pKa and values were determined, which revealed a photobasic character. Positive solvatochromism that resulted from specific interactions taking place in was studied using four different solvent scales, namely, Lippert-Mataga, Kamlet-Taft, Catalán and the recently proposed scale of Laurence et al., which yielded consistent results. Finally, theoretical calculations were conducted to analyze the mechanism of the probe in terms of natural transition orbitals (NTOs) and the spatial extent of charge transfer excitations.

Optical properties of two fluorene derived BODIPY molecular rotors as fluorescent ratiometric viscosity probes

Two fluorescent ratiometric fluorene derived BODIPY probes present a sensitive response to microviscosity changes.

Acid–base and coordination properties of 2-phenyl-3-hydroxy-4-quinolones in aqueous media

2-Phenyl-3-hydroxy-4-quinolones bind metal ions with selective fluorescence response in aqueous media.

Two fluorescent Schiff base sensors for Zn2+: the Zn2+/Cu2+ion interference

While theenol-iminetautomer inL1exhibits Zn²⁺/Cu²⁺ion interference, theketo-enaminetautomer inL2recognizes only Zn²⁺.

Thiourea derivatives and their nickel(II) and platinum(II) complexes: antifungal activity

We have synthesized two thiourea derivatives of methyl anthranilate (1, 2) and their complexes with nickel (3) and platinum(II) (4). We have also prepared the complexes of nickel(II) with two benzoylthiourea derivatives (5, 6). The obtained compounds were characterized by elemental analysis, spectroscopic methods (FT-IR, UV-vis, NMR), mass spectrometry and thermal analysis. Compound 1, C(20)H(23)N(3)O(2)S, crystallizes in monoclinic space group P21/n, with Z=4, and unit cell parameters, a=8.8042(4) A, b=7.6608(3) A, c=28.834(2) A, alpha=gamma=90 degrees, beta=90.94(1) degrees. Compound 2, C(20)H(21)N(3)O(3)S, crystallizes in monoclinic space group P21/c, with Z=4, and unit cell parameters, a=7.7345(4) A, b=8.6715(4) A, c=29.113(2) A, alpha=gamma=90 degrees, beta=90.67(1) degrees. Compound 5, C(24)H(30)N(4)NiO(2)S(2), crystallizes in monoclinic space group P21/n, with Z=4, and unit cell parameters, a=10.4317(8) A, b=18.517(2) A, c=13.299(1) A, alpha=gamma=90 degrees, beta=104.53(1) degrees. Compound 6, C(25)H(28)Cl(2)N(4)NiO(4)S(2), crystallizes with a molecule of CH(2)Cl(2) in triclinic space group P-1, with Z=2, and unit cell parameters, a=10.362(1) A, b=11.849(2) A, c=12.536(2) A, alpha=90.04(2) degrees, beta=84.73(1) degrees, gamma=113.43(2) degrees. Compounds 1 and 2 show antifungal activity against the major pathogens responsible for important plant diseases (Botrytis cinerea, Colletotrichum fragariae, Fusarium oxysporum and Phoma betae). The antifungal activity is practically the same for morpholine and ethyl derivatives.

Chromosomal insertions localized around oriC affect the cell cycle in Escherichia coli

The present work reports the effects of localized insertions around the origin of Escherichia coli chromosome, oriC, on cell cycle parameters. These insertions cause an increase of the C period with an inverse correlation to the distance from oriC. In addition, Omega insertion near oriC causes an increase in the number of replication forks per chromosome, n, and Tn10 insertion causes a decrease in growth rate. We found that the same insertion positioned in another region of the chromosome, outside of oriC, has a negligible effect on the C period. Marker frequency analysis suggests a slower replication velocity along the whole chromosome. We propose that the insertions positioned at less than 2 kbp from oriC could create a structural alteration in the origin of replication that would result in a longer C period. Flow cytometry reveals that asynchrony is not associated with these alterations.

Chloride and ethyl ester morpholine thiourea derivatives and their Ni(II) complexes. Crystal and molecular structures of the thiourea derivative L-leucine methyl ester and its complexes with Cu(II) and Pt(II). Growth of the pathogenic fungus Botrytis cinerea

We have synthesized a series of ligands (1, 3, 4, 6 and 7) and some of their complexes with Ni(II), Cu(II) and Pt(II) (2, 5, 8 and 9). These compounds were studied and characterized by elemental analysis, IR and UV-Vis spectra, conductivity measurements in solution, FAB+/MS, 1H and 13C NMR, ESR, etc. Compound 7 crystallized in the orthorhombic space group P2(1)2(1)2(1), with Z = 4. Unit cell parameters were as follows: a = 21.307(2) A, alpha = 90 degrees, b = 12.498(1) A, beta = 90 degrees, c = 7.7232(4) A, gamma = 90 degrees. For seven of these compounds, the antifungal activity of a major pathogen responsible for important crop damage was studied. In general, inhibition by the ligands was higher than that of the complexes. When the thiourea was linked to some diethyl groups, the compounds showed higher antifungal activity than the morpholine groups. Compound 3 achieved total inhibition (100%).

Determining the optimal thymidine concentration for growing Thy- Escherichia coli strains

Changes of thymidine concentration in the growth medium affect the chromosome replication time of Thy- strains without at the same time causing a detectable difference in the growth rate (R. H. Pritchard and A. Zaritsky, Nature 226:126-131, 1970). Consequently, the optimal thymidine concentration cannot be determined by ascertaining which concentration produces the highest growth rate. Here we present a method for determining the optimal thymidine concentration of any Thy- Escherichia coli strain. Using this method, we found that the E. coli "wild-type" strain MG1655 has a partial Thy- phenotype.

A temperature upshift induces initiation of replication at oriC on the Escherichia coli chromosome

A temperature upshift of 10 or more degrees in the growth temperature of a bacterial culture causes induction of extra rounds of chromosome replication. This heat-induced replication (HIR) initiates at oriC, is transitory, requires RNase H1 and RecA proteins and requires neither RNA polymerase activity nor de novo protein synthesis. The number of origins activated by heat is growth rate and temperature differential dependent. An origin activation higher than 20% increases the DNA:mass ratio around twofold, and this value is kept constant for the subsequent generations of growth at 41 C. We have also shown that HIR is neither related to SDR nor induced by the heat shock response. We suggest that a thermodynamic alteration of oriC structure or of membrane fluidity could explain the observed HIR.

On the origin and evolution of the genetic code

Two ideas have essentially been used to explain the origin of the genetic code: Crick's frozen accident and Woese's amino acid-codon specific chemical interaction. Whatever the origin and codon-amino acid correlation, it is difficult to imagine the sudden appearance of the genetic code in its present form of 64 codons coding for 20 amino acids without appealing to some evolutionary process. On the contrary, it is more reasonable to assume that it evolved from a much simpler initial state in which a few triplets were coding for each of a small number of amino acids. Analysis of genetic code through information theory and the metabolism of pyrimidine biosynthesis provide evidence that suggests that the genetic code could have begun in an RNA world with the two letters A and U grouped in eight triplets coding for seven amino acids and one stop signal. This code could have progressively evolved by making gradual use of letters G and C to end with 64 triplets coding for 20 amino acids and three stop signals. According to proposed evidence, DNA could have appeared after the four-letter structure was already achieved. In the newborn DNA world, T substituted U to get higher physicochemical and genetic stability.

A calcium-binding protein that may be required for the initiation of chromosome replication in Escherichia coli

Starvation for isoleucine but not for other amino acids in an ilv- strain or the addition of valine in an ilv+ strain inhibits initiation of chromosome and minichromosome replication in stringent (Rel+) Escherichia coli, but it does not inhibit replication in relaxed (relA) mutants (Guzman et al, 1988). From these results, we concluded that, (1) oriC initiation of replication is inhibited by ppGpp, and (2) isoleucine is not needed for the protein synthesis required at initiation. These results led us to find an isoleucine-free protein whose de novo synthesis is the sole protein synthesis requirement for oriC initiation. We also present evidence that this protein may be a calcium-binding protein located at 73 min in the genetic map.

The effect of nitrosoguanidine upon DNA synthesis in vitro

Both the polymerase and the exonuclease activities of DNA polymerase III are inactivated by treatment with nitrosoguanidine. The treatment of the DNA template with the mutagen does not affect the template in supporting DNA synthesis. No effect of nitrosoguanidine upon fidelity of replication in vitro was detected.

Mutation and DNA replication in Escherichia coli treated with low concentrations of N-methyl-N'-nitro-N-nitrosoguanidine

N-Methyl-N'-nitro-N-nitrosoguanidine (nitrosoguanidine) causes an unexpectedly high frequency of closely linked double mutants because of its specificity for chromosome regions in replication. Low nitrosoguanidine concentrations (I mug/ml) in liquid cultures allow replications at the normal rate and are mutagenic. It was expected that mutations would be spread over the chromosome as it replicated, but a high frequency of closely linked double mutants was found. If a thymine auxotroph is grown in the presence of 5-bromodeoxyuridine (BUdR) and nitrosoguanidine, then exposed to 313-nm radiation (which destroys BUdR-substituted DNA), the mutation frequency is much higher among survivors than among non-irradiated cells. It is concluded that nitrosoguanidine inhibits DNA replication in a small fraction of the population and that mutations are induced in that same fraction. Nitrosoguanidine treatment leads to a high frequency of closely linked double mutants under all known conditions.