Site-selective Modification
Site-selective Modification - Related Videos
08:48
Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment
0 Views •
Cited by 1 •
2015
We report on a process of in situ alteration of HF treated Si (001) surface into a hydrophilic or hydrophobic state by irradiating samples in microfluidic chambers filled with H2O2/H2O solution (0.01%-0.5%) or methanol solutions using pulsed UV laser of a relative low pulse fluence.
02:32
Histone Modification
0 Views •
2020
The histone proteins have a flexible N-terminal tail extending out from the nucleosome. These histone tails are often subjected to post-translational modifications such as acetylation, methylation, phosphorylation, and ubiquitination. Particular combinations of these modifications form “histone codes” that influence the chromatin folding and tissue-specific gene expression. Acetylation The enzyme histone acetyltransferase adds acetyl group to the histones. Another enzyme, histone deacetylase,...
02:25
Spreading of Chromatin Modifications
0 Views •
2020
The histone proteins in the nucleosomes are post-translationally modified (PTM) to increase or decrease access to DNA. The commonly observed PTMs are methylation, acetylation, phosphorylation, and ubiquitination of lysine amino acids in the histone H3 tail region. These histone modifications have specific meaning for the cell. Hence, they are called "histone code". The protein complex involved in histone modification is termed as "reader-writer" complex. Writers The writer is an enzyme that can...
07:08
Detection of Histone Modifications in Plant Leaves
0 Views •
Cited by 22 •
2011
A reliable and useful approach to detect histone modifications on specific plant genes is described. The approach combines chromatin immunoprecipitation (ChIP) and real-time quantitative PCR. It allows detection of histone modifications on specific genes with a role in diverse physiological processes.
06:48
Natural Selection - Concepts
0 Views •
2019
Fitness Widespread variation of phenotypes in natural populations provides the raw material for evolution, which is the change in the inherited traits of populations over successive generations. Natural selection is one of the main mechanisms of evolution and requires variable traits to be heritable and associated with differential survival and/or reproductive success. Phenotypes that correlate with greater success will have more offspring that survive to reproduce in the next generation, and...
FAQs
Steric accessibility and electronic environment help determine which molecular site reacts preferentially. A less crowded site may be easier for a reagent or catalyst to reach, while differences in electronic character can make one bond or functional group more favorable for reaction. Evaluating both factors allows chemists to predict and control competing pathways before choosing reaction conditions.
These components bias reactivity toward a desired molecular site. Catalysts can favor one bond-forming or bond-breaking pathway, whereas directing groups help position the reaction at a selected location. Protecting groups temporarily suppress reactivity elsewhere. Together, these strategies improve control when several similar functional groups could otherwise undergo competing chemical changes.
Reaction conditions influence which pathway is favored among chemically similar possibilities. By adjusting conditions to support a particular catalyst, directing group, protecting group, or local electronic and steric preference, chemists can increase the likelihood that the intended site reacts while other sites remain unchanged. This control is especially valuable in molecules containing multiple potentially reactive groups.
Planning begins by identifying the candidate reactive sites and comparing their steric accessibility and electronic environments. Chemists then determine whether a catalyst, directing group, protecting group, or carefully chosen reaction condition can favor the intended pathway. The selected strategy is evaluated by whether it produces the desired bond-forming or bond-breaking event without requiring unnecessary redesign of the molecule.
The approach is particularly useful during late-stage functionalization of complex molecules. It allows a preassembled structure to receive a targeted chemical change rather than being rebuilt through an extensive sequence. This can improve synthetic efficiency and is relevant to the preparation of pharmaceuticals, natural products, molecular probes, and advanced materials.
Beyond improving synthesis, selective modification can help researchers examine how an individual molecular site affects biological or material properties. Applying a controlled change to one location makes it possible to connect that structural alteration with the behavior of the larger molecule. This supports studies involving pharmaceuticals, natural products, probes, and advanced materials while limiting changes elsewhere.