pH-dependent absorption spectra of rhodopsin mutant E113Q: On the role of counterions and protein

2017 ◽  
Vol 174 ◽  
pp. 25-31 ◽  
Author(s):  
Peng Xie ◽  
Panwang Zhou ◽  
Ahmed Alsaedi ◽  
Yan Zhang
Keyword(s):  
Absorption Spectra ◽  
Dependent Absorption ◽  
Ph Dependent

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.

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

pH‐Dependent Degradation of Layered Black Phosphorus: Essential Role of Hydroxide Ions

2018 ◽  
Author(s):  
Siyu Zhang ◽  
Xuejiao Zhang ◽  
Lei Lei ◽  
Xue‐Feng Yu ◽  
Jingwen Chen ◽  
...  
Keyword(s):  
Essential Role ◽  
Black Phosphorus ◽  
Ph Dependent

Prediction of pH dependent absorption using in vitro, in silico, and in vivo rat models: Early liability assessment during lead optimization

2015 ◽  
Vol 76 ◽  
pp. 173-180 ◽  
Author(s):  
Ajay Saxena ◽  
Devang Shah ◽  
Shweta Padmanabhan ◽  
Shashyendra Singh Gautam ◽  
Gajendra Singh Chowan ◽  
...  
Keyword(s):  
In Silico ◽  
Lead Optimization ◽  
Rat Models ◽  
Dependent Absorption ◽  
Ph Dependent

scholarly journals Conformational Destabilization of Immunoglobulin G Increases the Low pH Binding Affinity with the Neonatal Fc Receptor

2015 ◽  
Vol 291 (4) ◽  
pp. 1817-1825 ◽  
Author(s):  
Benjamin T. Walters ◽  
Pernille F. Jensen ◽  
Vincent Larraillet ◽  
Kevin Lin ◽  
Thomas Patapoff ◽  
...  
Keyword(s):  
Binding Affinity ◽  
Hydrogen Exchange ◽  
Dissociation Constants ◽  
Conformational Dynamics ◽  
Fc Receptor ◽  
Salt Bridges ◽  
Neonatal Fc Receptor ◽  
Intermolecular Contacts ◽  
Ph Dependent

Crystallographic evidence suggests that the pH-dependent affinity of IgG molecules for the neonatal Fc receptor (FcRn) receptor primarily arises from salt bridges involving IgG histidine residues, resulting in moderate affinity at mildly acidic conditions. However, this view does not explain the diversity in affinity found in IgG variants, such as the YTE mutant (M252Y,S254T,T256E), which increases affinity to FcRn by up to 10×. Here we compare hydrogen exchange measurements at pH 7.0 and pH 5.5 with and without FcRn bound with surface plasmon resonance estimates of dissociation constants and FcRn affinity chromatography. The combination of experimental results demonstrates that differences between an IgG and its cognate YTE mutant vary with their pH-sensitive dynamics prior to binding FcRn. The conformational dynamics of these two molecules are nearly indistinguishable upon binding FcRn. We present evidence that pH-induced destabilization in the CH2/3 domain interface of IgG increases binding affinity by breaking intramolecular H-bonds and increases side-chain adaptability in sites that form intermolecular contacts with FcRn. Our results provide new insights into the mechanism of pH-dependent affinity in IgG-FcRn interactions and exemplify the important and often ignored role of intrinsic conformational dynamics in a protein ligand, to dictate affinity for biologically important receptors.

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.

Mechanistic Observations on the Role of the Stannous Ion in Caries Lesion De- and Remineralization

2016 ◽  
Vol 50 (4) ◽  
pp. 378-382 ◽  
Author(s):  
Frank Lippert
Keyword(s):  
Factorial Design ◽  
Surface Hardness ◽  
Acid Resistance ◽  
Design Studies ◽  
Mineral Distribution ◽  
Caries Lesion ◽  
Stannous Ion ◽  
Ph Dependent

Two mechanistic, laboratory, factorial design studies were conducted to investigate the effect of the stannous ion (Sn2+) in the absence or presence of fluoride on caries lesion de- and remineralization. Study I was concerned with determining changes in mineral distribution of subsurface lesions, whereas study II investigated changes in surface hardness of surface-softened lesions as a function of pH. Study I showed that Sn2+ modulates the effects of fluoride by preventing lamination. Study II revealed that the effect of Sn2+ on rehardening is pH dependent. Neither study demonstrated synergy between Sn2+ and fluoride, yet interactions were observed. Sn2+ does interfere with remineralization to some extent although it provided acid resistance. The role of Sn2+ in the caries process is complex.

scholarly journals Simulating Absorption Spectra of Flavonoids in Aqueous Solution: A Polarizable QM/MM Study

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5853
Author(s):  
Sulejman Skoko ◽  
Matteo Ambrosetti ◽  
Tommaso Giovannini ◽  
Chiara Cappelli
Keyword(s):  
Molecular Dynamics ◽  
Aqueous Solution ◽  
Hydrogen Bonding ◽  
Force Field ◽  
Absorption Spectra ◽  
Computational Study ◽  
Md Simulations ◽  
Quantum Mechanical ◽  
Hydrogen Bonding Interactions

We present a detailed computational study of the UV/Vis spectra of four relevant flavonoids in aqueous solution, namely luteolin, kaempferol, quercetin, and myricetin. The absorption spectra are simulated by exploiting a fully polarizable quantum mechanical (QM)/molecular mechanics (MM) model, based on the fluctuating charge (FQ) force field. Such a model is coupled with configurational sampling obtained by performing classical molecular dynamics (MD) simulations. The calculated QM/FQ spectra are compared with the experiments. We show that an accurate reproduction of the UV/Vis spectra of the selected flavonoids can be obtained by appropriately taking into account the role of configurational sampling, polarization, and hydrogen bonding interactions.

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