scholarly journals Coloration of Flowers by Flavonoids and Consequences of pH Dependent Absorption

2021 ◽  
Vol 11 ◽  
Author(s):  
Doekele G. Stavenga ◽  
Hein L. Leertouwer ◽  
Bettina Dudek ◽  
Casper J. van der Kooi
Keyword(s):  
Absorption Spectra ◽  
Ph Dependence ◽  
Bathochromic Shift ◽  
Flower Color ◽  
Color Evolution ◽  
Dependent Absorption ◽  
Ph Dependent ◽  
Basic States ◽  
Pigment Absorption ◽  
Derivatives Of

Flavonoid pigments are key determinants of flower colors. As absorption spectra of flavonoids are known to be severely pH-dependent, cellular pH will play a crucial role in flower coloration. The flavonoids are concentrated in the vacuoles of the flowers’ epidermal cells, and thus the pigments’ absorption spectra are modulated by the vacuolar pH. Here we study the pH dependence of flavonoid absorption spectra in extracts from flowers of two poppy species Papaver dubium (red) and Meconopsis cambrica (orange), and a white and red Mandevilla sanderi variety. In the red poppy and Mandevilla flowers, absorption spectra of the cyanidin- and pelargonidin-based anthocyanins peak in the blue-green-wavelength range at low pH, but exhibit a distinct bathochromic shift at higher pH. This shift to longer wavelengths is not found for the blue-absorbing nudicaulin derivatives of M. cambrica, which have a similar absorption spectrum at low and high pH. The pH-dependent absorption changes of the white M. sanderi’s flavonoid remained restricted to the UV. An analysis of the spectra with logistic functions suggests that the pH-dependent characteristics of the basic states of flavonols and anthocyanins are related. The implications of tuning of pH and pigment absorption spectra for studies on flower color evolution are discussed.

Molecular Packing-Dependent Exciton and Polariton Dynamics in Anthradithiophene Organic Crystals

MRS Advances ◽  
2018 ◽  
Vol 3 (59) ◽  
pp. 3465-3470 ◽  
Author(s):  
Jonathan D B Van Schenck ◽  
Gregory Giesbers ◽  
Akash Kannegulla ◽  
Li-Jing Cheng ◽  
John E. Anthony ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Energy Absorption ◽  
Absorption Spectra ◽  
Organic Crystals ◽  
Optical Microcavities ◽  
Enhanced Absorption ◽  
Excitonic Transition ◽  
Dependent Absorption ◽  
Derivatives Of ◽  
Primary Contribution

AbstractPolarization-dependent absorption spectra of two functionalized derivatives of fluorinated anthradithiophene, diF TES-ADT and diF TDMS-ADT, were studied in the crystal phase using a Holstein-like Hamiltonian. For both molecules, the primary contribution to the lowest energy absorption was found to be the S0-S1 excitonic transition perturbed by an intermolecular coupling of 15 meV for both TES and TDMS. A secondary contribution, consistent with that from charge-transfer states, was also found. Additionally, absorption spectra were analysed when crystals were placed inside of optical microcavities formed by two metal mirrors. Cavities exhibited a primary absorption peak determined to be an enhanced absorption from the lowest-energy S0-S1 transition.

Rationalizing the pH-Activity Response for Escherichia Coli’s Glycinamide Ribonucleotidetransformylase Through Computational Methods

2019 ◽  
Author(s):  
Adrian Roitberg ◽  
Pancham Lal Gupta
Keyword(s):  
Transfer Reaction ◽  
Catalytic Mechanism ◽  
Ph Dependence ◽  
Ph Effects ◽  
Dependent Manner ◽  
E Coli ◽  
Gar Tfase ◽  
Activity Curve ◽  
Ph Dependent ◽  
Formyl Transfer

<div>Human Glycinamide ribonucleotide transformylase (GAR Tfase), a regulatory enzyme in the de novo purine biosynthesis pathway, has been established as an anti-cancer target. GAR Tfase catalyzes the formyl transfer reaction from the folate cofactor to the GAR ligand. In the present work, we study E. coli GAR Tfase, which has high sequence similarity with the human GAR Tfase with most functional residues conserved. E. coli GAR Tfase exhibits structural changes and the binding of ligands that varies with pH which leads to change the rate of the formyl transfer reaction in a pH-dependent manner. Thus, the inclusion of pH becomes essential for the study of its catalytic mechanism. Experimentally, the pH-dependence of the kinetic parameter kcat is measured to evaluate the pH-range of enzymatic activity. However, insufficient information about residues governing the pH-effects on the catalytic activity leads to ambiguous assignments of the general acid and base catalysts and consequently its catalytic mechanism. In the present work, we use pH-replica exchange molecular dynamics (pH-REMD) simulations to study the effects of pH on E. coli GAR Tfase enzyme. We identify the titratable residues governing the pH-dependent conformational changes in the system. Furthermore, we filter out the protonation states which are essential in maintaining the structural integrity, keeping the ligands bound and assisting the catalysis. We reproduce the experimental pH-activity curve by computing the population of key protonation states. Moreover, we provide a detailed description of residues governing the acidic and basic limbs of the pH-activity curve.</div>

scholarly journals Association-dependent absorption spectra of oxyhemoglobin A and its subunits.

1981 ◽  
Vol 256 (15) ◽  
pp. 7917-7924 ◽  
Author(s):  
J.S. Philo ◽  
M.L. Adams ◽  
T.M. Schuster
Keyword(s):  
Absorption Spectra ◽  
Dependent Absorption

Absorption Spectra of Substituted 2-Phenylindan-1,3-Dion-2-YL Radicals in Solution

1983 ◽  
Vol 38 (12) ◽  
pp. 1337-1341
Author(s):  
J. Zechner ◽  
N. Getoff ◽  
I. Timtcheva ◽  
F. Fratev ◽  
St. Minchef
Keyword(s):  
Free Energy ◽  
Absorption Spectra ◽  
Flash Photolysis ◽  
Bathochromic Shift ◽  
Substitution Effects ◽  
Linear Free Energy Relationship ◽  
Linear Free Energy

Abstract Flash photolysis of a series of 2-phenylindandione-1,3 derivatives substituted in the 4′ position results in both the formation of stable benzylidenephthalides and of phenylindan-1,3-dion-2-yl radicals. The u. v. absorption maxima of these radicals are dependent on the solvent and show a bathochromic shift upon substitution. These substitution effects were correlated by means of a linear free energy relationship. Attempts were made to draw conclusions concerning the changes in the gap of the states involved and their curvature due to substitution.

Quinoline-annulated chlorins and chlorin-analogs

2016 ◽  
Vol 20 (01n04) ◽  
pp. 265-273 ◽  
Author(s):  
Joshua Akhigbe ◽  
Mengxi Yang ◽  
Michael Luciano ◽  
Christian Brückner
Keyword(s):  
Absorption Spectra ◽  
Functional Group ◽  
Bathochromic Shift ◽  
Red Shift ◽  
Simple Strategy

The OsO4-mediated dihydroxylation of quinoline-annulated porphyrin generates a quinoline-annulated dihydroxychlorin in a regioselective fashion. Its dihydroxypyrroline moiety, located at the opposite of the annulated pyrrole, is susceptible to the same functional group interconversions we previously demonstrated for non-annulated dihydroxychlorins: oxidations to the corresponding dione, lactone, and dialkoxymorpholine derivatives. The quinoline-annulated chlorin and derivatives are all characterized by absorption spectra that are much broadened and between 130 and 220 nm red-shifted compared to their non-annulated analogs. Absorbance maxima in the NIR up to well above 800 nm were recorded. We attribute the bathochromic shift to their extended [Formula: see text]-systems and inferred non-planarity, highlighting that quinoline-annulation is a particularly effective and simple strategy to red-shift the absorption spectra of chlorins and chlorin analogs.

Enhanced Analytic Approach for Describing pH Triggered Fast Drug Release Systems

2021 ◽  
Vol 18 ◽  
Author(s):  
Aykut Elmas ◽  
Guliz Akyuz ◽  
Ayhan Bergal ◽  
Muberra Andac ◽  
Omer Andac
Keyword(s):  
Drug Release ◽  
Ph Dependence ◽  
Slope Angle ◽  
Ph Sensitive ◽  
Analytic Model ◽  
Two Dimensional ◽  
Analytic Equation ◽  
One Dimensional ◽  
Ph Dependent ◽  
Fast Release

Background: pH sensitive dendrimers attached to nanocarriers, as one of the drug release systems, has become quite popular due to their ease of manufacture in experimental conditions and ability to generate fast drug release in the targeted area. This kind of fast release behavior cannot be represented properly most of the existing kinetic mathematical models. Besides, these models have either no pH dependence or pH dependence added separately. So, they have remained one dimensional. Objective: The aim of this study was to establish the proper analytic equation to describe the fast release of drugs from pH sensitive nanocarrier systems. Then, to combine it with the pH dependent equation for establishing a two-dimensional model for whole system. Methods: We used four common kinetic models for comparison and we fitted them to the release data. Finding that, only Higuchi and Korsmeyer-Peppas models show acceptable fit results. None of these models have pH dependence. To get a better description for pH triggered fast release, we observed the behavior of the slope angle of the release curve. Then we puroposed a new analytic equation by using relation between the slope angle and time. Result: To add a pH dependent equation, we assumed the drug release is “on” or “off” above/below specific pH value and we modified a step function to get a desired behavior. Conclusion: Our new analytic model shows good fitting, not only one-dimensional time dependent release, but also two-dimensional pH dependent release, that provides a useful analytic model to represent release profiles of pH sensitive fast drug release systems.

scholarly journals Systematic exploration of the pH dependence of a peptide hydrogel

2019 ◽  
Vol 97 (6) ◽  
pp. 430-434 ◽  
Author(s):  
Natashya Falcone ◽  
Tsuimy Shao ◽  
Xiaoyi Sun ◽  
Heinz-Bernhard Kraatz
Keyword(s):  
Mechanical Strength ◽  
Narrow Range ◽  
Ph Dependence ◽  
Stimuli Responsive ◽  
Systematic Exploration ◽  
Ph Conditions ◽  
Ph Dependent ◽  
Functional Biomaterials ◽  
Peptide Hydrogel

Stimuli-responsive peptide gels are a growing class of functional biomaterials that are involved in many applications in research. Here, we present a novel di-peptide hydrogel from the compound Boc–Phe–Trp–OH in various buffer and pH conditions. We examine the effects of different stimuli, including temperature and pH, on the mechanical strength of the gels through frequency rheology studies. We found that this hydrogelator is highly pH dependent, only forming a gel in a narrow range of pH 6–7. This hydrogelator hold promise for the development of new stimuli-responsive biomaterials for specific applications that require this type of specific stimuli.

Sign in / Sign up

Export Citation Format

Share Document