ABSTRACT
Single-molecule localization microscopy (SMLM) enables the visualization of biomolecules at unprecedented resolution and requires control of the fluorescent blinking (ON/OFF) states of fluorophores to detect single-molecule fluorescence without overlapping of the signals. Although SMLM probes based on the intramolecular spirocyclization of Si-xanthene fluorophores have been developed, fluorophores with lower ON/OFF ratios are required for SMLM visualization of high-density structures. Here, we describe a silinane structure that lowers the ON/OFF ratio of Si-xanthene fluorophores. On the basis of Mulliken population analysis, we replaced the dimethylsilane moiety in Si-rhodamine with a silinane moiety to increase the partial charge at the 9-position of the carbon atom in the Si-xanthene ring and to promote the ring-closure reaction. Evaluation of fluorescence properties in a solution and in single-molecule imaging indicated that introducing the silinane sufficiently stabilized the nonfluorescent spirocyclic forms, thus decreasing the fluorescence ON/OFF ratio. This novel substitution was applied to Si-rhodamines with various amine structures and to an Si-fluorescein to expand the color palette. We demonstrated SMLM observation of microtubules in fixed HeLa cells using the developed fluorophores in two color channels. The results demonstrated the feasibility of extending the design strategies of SMLM probes based on Si-xanthenes through modification of the substituents on the Si atom.
Subject(s)
Fluorescent Dyes , Microscopy , Fluoresceins , HeLa Cells , Humans , RhodaminesABSTRACT
Dysfunction of glutamatergic neurotransmission has been implicated in the pathogenesis of epilepsy and numerous other neurological diseases. Here we describe the discovery of a series of 1,3,5-triaryl-1H-pyridin-2-one derivatives as noncompetitive antagonists of AMPA-type ionotropic glutamate receptors. The structure-activity relationships for this series of compounds were investigated by manipulating individual aromatic rings located at positions 1, 3, and 5 of the pyridone ring. This culminated in the discovery of 2-(2-oxo-1-phenyl-5-pyridin-2-yl-1,2-dihydropyridin-3-yl)benzonitrile (perampanel, 6), a novel, noncompetitive AMPA receptor antagonist that showed potent activity in an in vitro AMPA-induced Ca2+ influx assay (IC50=60 nM) and in an in vivo AMPA-induced seizure model (minimum effective dose of 2 mg/kg po). Perampanel is currently in regulatory submission for partial-onset seizures associated with epilepsy.
Subject(s)
Drug Discovery , Pyridones/chemistry , Pyridones/pharmacology , Receptors, AMPA/antagonists & inhibitors , Animals , Biological Availability , Half-Life , High-Throughput Screening Assays , In Vitro Techniques , Magnetic Resonance Spectroscopy , Male , Mice , Nitriles , Pyridones/pharmacokinetics , Rats , Structure-Activity RelationshipABSTRACT
A series of novel neuronal voltage-dependent calcium channel (VDCC) blockers, with inhibitory activity at low micromolar and moderate solubility in water, was discovered by constructing and screening a focused library based on emopamil (1) left hand (ELH) as a bioactive template.
Subject(s)
Calcium Channel Blockers/chemistry , Calcium Channel Blockers/pharmacology , Calcium Channels, N-Type/drug effects , Synaptosomes/drug effects , Verapamil/analogs & derivatives , Verapamil/chemistry , Animals , Combinatorial Chemistry Techniques , Ion Channel Gating/drug effects , Piperazines/chemistry , Rats , Solubility , Stereoisomerism , Structure-Activity Relationship , Synaptosomes/metabolismABSTRACT
An asymmetric synthesis of (2S)-2-(2-isopropyl)-5-hydroxy-2-phenylpentanenitrile (emopamil left hand, 2) has been completed by use of the MAD (methyl aluminum bis(4-methyl-2,6-di-tert-butylphenoxide)-induced rearrangement of a chiral epoxyalcohol as the key reaction. The stereochemistry of the chiral quaternary center was confirmed by transformation of 2 to (S)-noremopamil. This method requires minimal purification procedures and affords high chemical and optical yields. Acid-catalyzed isomerization of an allylaldehyde and retro-aldol type racemization at the quaternary carbon of a nitrile-alcohol were encountered.
Subject(s)
Verapamil/analogs & derivatives , Verapamil/chemical synthesis , Catalysis , Chemistry, Organic/methods , Chromatography, High Pressure Liquid , Magnetic Resonance Spectroscopy , Molecular Structure , Organometallic Compounds/chemistry , Stereoisomerism , Verapamil/chemistryABSTRACT
7-Substituted norbornadienes were stereoselectively converted into the meso-3,5-bis(acetoxymethyl)cyclopentenes by a three-step sequence of ozonolysis, reduction, and acetylation. Rhizopus delemar lipase (RDL)-catalyzed asymmetric hydrolysis of meso-3,5-bis(acetoxymethyl)cyclopentenes afforded the monoalcohols of high enantiomeric purities (>95% ee) in good yields (64-95%). The obtained monoalcohols 11 and 14 could be applied for the synthesis of antiviral carbocyclic nucleosides (-)-carbovir and (-)-BCA.
