Correlation between PAL, medicarpin, phenol and flavonoid content in Medicago sativa L. at different growth stages

Alfalfa (Medicago sativa L.) is from Fabaceae family that has several flavonoid compound in roots and shoots. in alfalfa the major phytoalexin is medicarpin. In this study, total phenolic and flavonoid compounds and phenylalanin ammonia lyase (PAL) activity in different stages of development were measured. In this research the concentration of medicarpin by HPLC were studied in different stages of development. The lowest and highest level of the concentration of medicapin were in seedling stage and budding stage of growth, respectively. The results indicated that contents of total phenolic compounds and total flavonoid and PAL activity increase with developmental stage ,but decrease in flowering stage of growth

Mechanosensitive membrane probes: emphasis on stable, modifiable and target-specific headgroups

Our group developed a new class of mechanosensitive membrane probes. To ensure the partitioning and the correct orientation inside the membrane, a charged "head" group was added to the design, generating an amphiphilic probe. Since the original design proven to show high mechanophoric properties the main focus was directed towards the hydrophilic part of the probe, the "head" group. A series of different linkers between the charged "head" group and the DTT core were tested resulting in the synthesis of a new probe which retained the mechanophoric properties of the original probe all while increasing its bio­compatibility and chemical and photo­ stability. Furthurmore, Dynamic covalent boronate ester was used in order to specifically target gangliosides on model membranes. The responsiveness of ganglioside recognition was tested by monitoring the incorporation of the probe inside large unilamellar vesicles containing different concentrations of ganglioside. pH­-dependence of this recognition was assessed

Mechanosensitive Membrane Probes

This article assembles pertinent insights behind the concept of planarizable push–pull probes. As a response to the planarization of their polarized ground state, a red shift of their excitation maximum is expected to report on either the disorder, the tension, or the potential of biomembranes. The combination of chromophore planarization and polarization contributes to various, usually more complex processes in nature. Examples include the color change of crabs or lobsters during cooking or the chemistry of vision, particularly color vision. The summary of lessons from nature is followed by an overview of mechanosensitive organic materials. Although often twisted and sometimes also polarized, their change of color under pressure usually originates from changes in their crystal packing. Intriguing exceptions include the planarization of several elegantly twisted phenylethynyl oligomers and polymers. Also mechanosensitive probes in plastics usually respond to stretching by disassembly. True ground-state planarization in response to molecular recognition is best exemplified with the binding of thoughtfully twisted cationic polythiophenes to single- and double-stranded oligonucleotides. Molecular rotors, en vogue as viscosity sensors in cells, operate by deplanarization of the first excited state. Pertinent recent examples are described, focusing on λ-ratiometry and intracellular targeting. Complementary to planarization of the ground state with twisted push–pull probes, molecular rotors report on environmental changes with quenching or shifts in emission rather than absorption. The labeling of mechanosensitive channels is discussed as a bioengineering approach to bypass the challenge to create molecular mechanosensitivity and use biological systems instead to sense membrane tension. With planarizable push–pull probes, this challenge is met not with twistome screening, but with “fluorescent flippers,” a new concept to insert large and bright monomers into oligomeric probes to really feel the environment and also shine when twisted out of conjugation

Ganglioside-Selective Mechanosensitive Fluorescent Membrane Probes

The development of fluorescent probes to image forces in cells is an important challenge in chemistry and biology. Planarizable push‐pull probes have been introduced recently for this purpose. To provide most valuable information on forces in complex systems, these mechanosensitive ‘flipper' probes will have to be localized by molecular recognition of targets of interest. Here we report fluorescent flippers that selectively recognize gangliosides on the surface of lipid bilayer membranes by formation of dynamic covalent boronate esters. The original flipper probes were equipped with 2‐fluorophenyl boronic acids and benzoboroxoles using consecutive triazole and oxime ligation. Evaluation was done in large unilamellar vesicles composed of EYPC/SM/CL/GM 40:40‐x:20:x to obtain mixed membranes with separate liquid‐disordered (Ld) and ganglioside (GM) containing liquid‐ordered (Lo) domains. With increasing GM concentration, fluorescence intensities increased and excitation maximum shifted to the red. Deconvolution of the spectra confirmed that these changes originate from a migration of the flipper probes from Ld to Lo domains upon binding to the gangliosides and thus the planarization in the more ordered environment. Control mechanophores without boronic acids failed to show the same response, and fructose partially inhibited the ganglioside sensitivity. These results demonstrate that it is possible to selectively accumulate mechanosensitive flipper probes in Lo domains and, more generally, that probe localization in complex membranes is possible and matters

Detecting order and lateral pressure at biomimetic interfaces using a mechanosensitive second-harmonic-generation probe

A planarizable push–pull molecular probe with mechanosensitive properties was investigated at several biomimetic interfaces, consisting of different phospholipid monolayers located between dodecane and an aqueous buffer solution, using the interface-specific surface-second-harmonic-generation (SSHG) technique. Whereas the SSHG spectra recorded at liquid-disordered interfaces were similar to the absorption spectra in bulk solutions, those measured at liquid-ordered phases exhibited a remarkable shift towards lower energies to an extent depending on the surface pressure of the phospholipid monolayer. On the basis of quantum-chemical calculations, this effect was accounted for by the planarization of the mechanosensitive probe. Polarization-resolved SSHG measurements revealed that the average orientation of the probe at the interface is an even more sensitive reporter of lateral pressure and order than the spectral shape. Additionally, time-resolved SSHG measurements pointed to slower dynamics upon intercalation inside the phospholipid monolayer, most likely due to the more constrained environment. This study demonstrates that the concept of mechanosensitive optical probes can be further exploited when combined with a surface-selective nonlinear optical technique

Turn-On Sulfide Donors: An Ultrafast Push for Twisted Mechanophores

Attached to electron-rich aromatic systems, sulfides are very weak acceptors; however, attached to electron-poor aromatics, they turn into quite strong donors. Here, we show that this underappreciated dual nature of sulfides deserves full consideration for the design of functional systems. Tested with newly designed and synthesized planarizable push−pull mechanophores, sulfide acceptors in the twisted ground state are shown to prevent oxidative degradation and promote blue-shifting deplanarization. Turned on in the planar excited state, sulfide donors promote red-shifting polarization. Impressive Stokes shifts are the result. Demonstrating the usefulness of time-resolved broadband emission spectra to address significant questions, direct experimental evidence for the ultrafast (3.5 ps), polarity-independent and viscosity-dependent planarization from the twisted Franck−Condon S1 state to the relaxed S1 state could be secured

Headgroup engineering in mechanosensitive membrane probes

Systematic headgroup engineering yields planarizable push–pull flipper probes that are ready for use in biology – stable, accessible, modifiable –, and affords non-trivial insights into chalcogen-bond mediated mechanophore degradation and fluorescence enhancement

A Collection of Fullerenes for Synthetic Access Toward Oriented Charge-Transfer Cascades in Triple-Channel Photosystems

The development of synthetic methods to build complex functional systems is a central and current challenge in organic chemistry. This goal is important because supramolecular architectures of highest sophistication account for function in nature, and synthetic organic chemistry, contrary to high standards with small molecules, fails to deliver functional systems of similar complexity. In this report, we introduce a collection of fullerenes that is compatible with the construction of multicomponent charge-transfer cascades and can be placed in triple-channel architectures next to stacks of oligothiophenes and naphthalenediimides. For the creation of this collection, modern fullerene chemistry—methanofullerenes and 1,4-diarylfullerenes—is combined with classical Nierengarten–Diederich–Bingel approaches