Isotopic fractionation in proteins as a measure of hydrogen bond length

If a deuterated molecule containing strong intramolecular hydrogen bonds is placed in a hydrogenated solvent it may preferentially exchange deuterium for hydrogen. This preference is due to the difference between the vibrational zero-point energy for hydrogen and deuterium. It is found that the associated fractionation factor $\Phi$ is correlated with the strength of the intramolecular hydrogen bonds. This correlation has been used to determine the length of the H-bonds (donor-acceptor separation) in a diverse range of enzymes and has been argued to support the existence of short low-barrier H-bonds. Starting with a potential energy surface based on a simple diabatic state model for H-bonds we calculate $\Phi$ as a function of the proton donor-acceptor distance $R$. For numerical results, we use a parameterization of the model for symmetric O-H.... O bonds. We consider the relative contributions of the O-H stretch vibration, O-H bend vibrations (both in plane and out of plane), tunnelling splitting effects at finite temperature, and the secondary geometric isotope effect. We compare our total $\Phi$ as a function of $R$ with NMR experimental results for enzymes, and in particular with an empirical parametrisation $\Phi(R)$, used previously to determine bond lengths.Comment: Final version, accepted for publication in Journal of Chemical Physics. Minor changes, including more extensive discussion of relevant of model to protein

Effect of quantum nuclear motion on hydrogen bonding

This work considers how the properties of hydrogen bonded complexes, D-H....A, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (D) and acceptor (A) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O-H....O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4-3.0 A, i.e., from strong to weak bonds. The position of the proton and its longitudinal vibrational frequency, along with the isotope effects in both are discussed. An analysis of the secondary geometric isotope effects, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of the bending modes in also considered: their quantum effects compete with those of the stretching mode for certain ranges of H-bond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several experimental trends.Comment: 12 pages, 8 figures. Notation clarified. Revised figure including the effect of bending vibrations on secondary geometric isotope effect. Final version, accepted for publication in Journal of Chemical Physic

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Response of Yield and Fruit Quality to Foliar Application of Micronutrients in Lemon [Citrus limon (L.) Burm.] cv. Assam Lemon

Assam lemon [Citrus limon (L.) Burm.], an indigenous lemon cultivar of Assam, is widely cultivated in warm southern slopes of the Himalayas in North-Eastern India. Since this cultivar of lemon is having a prominent trait of bearing fruits in several flushes throughout the year, it is essential to provide sufficient nutrition for obtaining optimum yield with good quality fruits. In the current experiment, a randomized block design having twelve treatments with three replications was followed to find out the response of lemon fruit yield and quality to foliar application of micronutrients during the year 2019. Among all, the treatment ZnSO4 (0.2%) + FeSO4 (0.2%) + Borax (0.2%) + CuSO4 (0.2%) gave the best performance in improving the yield and quality of fruits. The highest number of fruits per plant at the time of harvesting (73), yield per plant (11.5 kg), fruit fresh weight (158 g), fruit length (9.60 cm), fruit diameter (5.80 cm), juice content (152 mL/fruit), TSS (6.40 °B), ascorbic acid (49.10 mg/100g), total sugar (6.30%), reducing sugar (3.90%), non-reducing sugar (2.40%) with lowest titratable acidity(3.13%) were obtained which revealed that the yield and fruit quality of lemon depends on the application of different micronutrients

Response of Yield and Fruit Quality to Foliar Application of Micronutrients in Lemon [Citrus limon (L.) Burm.] cv. Assam Lemon

Assam lemon [Citrus limon (L.) Burm.], an indigenous lemon cultivar of Assam, is widely cultivated in warm southern slopes of the Himalayas in North-Eastern India. Since this cultivar of lemon is having a prominent trait of bearing fruits in several flushes throughout the year, it is essential to provide sufficient nutrition for obtaining optimum yield with good quality fruits. In the current experiment, a randomized block design having twelve treatments with three replications was followed to find out the response of lemon fruit yield and quality to foliar application of micronutrients during the year 2019. Among all, the treatment ZnSO4 (0.2%) + FeSO4 (0.2%) + Borax (0.2%) + CuSO4 (0.2%) gave the best performance in improving the yield and quality of fruits. The highest number of fruits per plant at the time of harvesting (73), yield per plant (11.5 kg), fruit fresh weight (158 g), fruit length (9.60 cm), fruit diameter (5.80 cm), juice content (152 mL/fruit), TSS (6.40 °B), ascorbic acid (49.10 mg/100g), total sugar (6.30%), reducing sugar (3.90%), non-reducing sugar (2.40%) with lowest titratable acidity (3.13%) were obtained which revealed that the yield and fruit quality of lemon depends on the application of different micronutrients

Genes of Microorganisms: Paving Way to Tailor Next Generation Fungal Disease Resistant Crop Plants

The automation of sequencing technologies, flooding in the knowledge of plant-pathogen interactions and advancements in bioinformatics provide tools leading to better knowledge not only of the genome of plant pathogens or microorganism beneficial to plants but also of ways of incorporating genes from microbes into plants as microbial-derived resistance. The identification of various microorganism genes playing key role during pathogensis and the dissection of the signal transduction components of the hypersensitive response and systemic acquired resistance pathways have greatly increased the diversity of options available for tailoring fungus resistant crops. The genetically engineered plants carrying these genes showed spontaneous activation of different defense mechanisms, leading the plant in an elevated state of defense. This defense mode greatly enhances the plants ability to quickly react to a pathogen invasion and more successfully overcome the infection. The aim of this review is to highlight the dynamic use of genes of microorganisms in enhancing crop tolernace towards fungal intruders by examining the most relevant research in this field