Restricted Rotation
Restricted Rotation - Related Videos
09:45
Restriction Enzyme Digests
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2023
Restriction enzymes or endonucleases recognize and cut DNA at a specific sequence. These enzymes occur naturally in bacteria as a defense against bacteriophages - viruses that infect bacteria. Bacterial restriction enzymes cut the invading bacteriophage DNA while leaving the bacterial genomic DNA unharmed due to addition of methyl groups. This video explains the basic principles of restriction enzymes including: how restriction enzymes are named and the types of recognition sites and...
05:56
Mental Rotation
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2023
Source: Laboratory of Jonathan Flombaum—Johns Hopkins University Visual mental imagery refers to the ability to conjure images in one’s mind’s eye. This allows people to process visual material above and beyond the constraints of a current point-of-view; for example, a person could imagine, using their mind’s eye, how something might look in a different color, or what it would look like if it were made from a different material or rotated and seen from a different perspective. Mental imagery...
13:24
DNA Isolation and Restriction Enzyme Analysis - Student Protocol
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2019
DNA Isolation ExpandNOTE: In this experiment you will perform DNA isolation under two experimental conditions: one using a buffer containing the detergent SDS and one without detergent. Hypotheses: The alternate hypothesis for this experiment might be that the sample prepared without SDS, a strong anionic detergent that breaks apart cell membranes, will yield less DNA than the sample prepared with SDS. The null hypothesis for this experiment might be that both samples will yield an equal amount...
04:46
DNA Isolation and Restriction Enzyme Analysis - Concepts
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2019
The revelation of DNA as the hereditary molecule in all organisms has led to enormous scientific and medical breakthroughs and significantly enhanced our understanding of ourselves and other organisms. DNA isolation and profiling have been the fundamental first steps for many of the advancements in the past century; from identification of gene function, to revolutions of agriculture and forensics. Isolating DNA from Cells DNA isolation is a fairly simple procedure that requires few but...
07:48
Rotational Inertia
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2023
Source: Nicholas Timmons, Asantha Cooray, PhD, Department of Physics & Astronomy, School of Physical Sciences, University of California, Irvine, CA Inertia is the resistance of an object to being accelerated. In linear kinematics, this concept is directly related to the mass of an object. The more massive an object, the more force is required to accelerate that object. This is seen directly in Newton's second law, which states that force is equal to mass times acceleration. For rotation,...
FAQs
A rotational barrier represents the energy required to change a bond’s dihedral angle. If available energy is insufficient, the molecule remains near particular conformations; if the barrier is overcome, interconversion can occur. Thus, the barrier height controls whether conformers rapidly interchange or remain distinguishable under the conditions being considered.
Partial double-bond character gives the bond greater rigidity than a typical single bond. Rotation would disrupt the bonding arrangement associated with that character, so additional energy is required to change the dihedral angle. This restriction favors a planar amide arrangement and helps explain why amides behave differently from freely rotating single-bond systems.
Bulky substituents hinder rotation through steric repulsion, meaning that groups collide or approach unfavorable positions as the dihedral angle changes. Partial double-bond character instead restricts rotation through the electronic nature of the bond. Both effects raise the rotational barrier, but they can arise from different structural features and should be considered separately when interpreting molecular shape.
If the rotational barrier is high enough, interconversion between arrangements may become sufficiently slow that the forms behave as configurationally stable isomers. Lower barriers generally permit conformational interchange, whereas higher barriers preserve distinct arrangements. This distinction matters because restricted rotation can affect whether different molecular forms are merely transient shapes or experimentally distinguishable species.
Chemists examine the structural features that raise the rotational barrier, including partial double-bond character and steric repulsion, then consider the conformations those barriers favor. The resulting shapes can influence how a molecule reacts because reactive groups may be held in particular spatial arrangements. Restricted rotation therefore connects bonding features with both structure and reaction behavior.
Restricted rotation can slow exchange between molecular arrangements, allowing conformational or configurational differences to influence observed NMR signal patterns. Instead of treating every bond as freely mobile, interpretation must account for the possibility that groups occupy distinct environments for meaningful periods. This makes rotational behavior an important structural clue when analyzing molecular spectra.
Biologically important molecules often depend on defined three-dimensional shapes and on the relative positioning of functional groups. Restricted rotation can stabilize preferred conformations or preserve distinct arrangements, thereby influencing molecular structure and function. Its role is especially significant where amide planarity, conformational preferences, or slow interconversion affect how a molecule presents its reactive features.