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Related Concept Videos

Positive and Negative Feedback Loops01:18

Positive and Negative Feedback Loops

Animal organs and organ systems constantly adjust to internal and external changes through a process called homeostasis ("steady state"). Examples of these changes include regulation of the level of glucose or calcium in the blood or internal responses to external temperatures. Homeostasis requires  maintaining an internal dynamic equilibrium:
Cell Signaling Feedback Loops01:07

Cell Signaling Feedback Loops

Positive and negative feedback loops are crucial for regulating biological signaling systems. These feedback loops are processes that connect output signals to their inputs.
Negative feedback loops
Most signaling systems have negative feedback loops that can perform different functions such as output limiter, and adaptation.
Output limiter
Upon receiving an input signal, the cellular response rapidly increases until a threshold is reached. Beyond this threshold, a negative feedback loop...
Amplifying Signals via Enzymatic Cascade01:22

Amplifying Signals via Enzymatic Cascade

When a ligand binds to a cell-surface receptor, the receptor's intracellular domain changes shape, which may either activate its enzyme function or allow its binding to other molecules. The initial signal is amplified by most signal transduction pathways. This means that a single ligand molecule can activate multiple molecules of a downstream target. Proteins that relay a signal are most commonly phosphorylated at one or more sites, activating or inactivating the protein. Kinases catalyze the...
Negative and Positive Feedback01:18

Negative and Positive Feedback

Animal organs and organ systems constantly adjust to internal and external changes through a process called homeostasis ("steady state"). Examples of these changes include regulation of the level of glucose or calcium in the blood or internal responses to external temperatures. Homeostasis requires  maintaining an internal dynamic equilibrium:
Root Loci for Positive-Feedback Systems01:23

Root Loci for Positive-Feedback Systems

The Hartley oscillator is a positive feedback system that sustains oscillations by feeding the output back to the input in phase, thereby reinforcing the signal. Positive feedback systems can be viewed as negative feedback systems with inverted feedback signals. In these systems, the root locus encompasses all points on the s-plane where the angle of the system transfer function equals 360 degrees.
The construction rules for the root locus in positive feedback systems are similar to those in...
Amplifying Signals via Second Messengers01:15

Amplifying Signals via Second Messengers

Many receptor binding ligands are hydrophilic; they do not cross the cell membrane but bind to cell-surface receptors. Thus, their message must be relayed by second messengers present in the cell cytoplasm. There are several second messenger pathways, each with its own way of relaying information. For example, the G protein-coupled receptors can activate both phosphoinositol and cyclic AMP (cAMP) second messenger pathways. The phosphoinositol pathway is active when the receptor induces...

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Reliably Engineering and Controlling Stable Optogenetic Gene Circuits in Mammalian Cells
09:20

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Published on: July 6, 2021

A modular positive feedback-based gene amplifier.

Goutam J Nistala1, Kang Wu2, Christopher V Rao2

  • 1Department of Agricultural and Biological Engineering, University of Illinois at Urbana-Champaign, 1304 W Pennsylvania Ave, Urbana, IL, 61801, USA.

Journal of Biological Engineering
|March 2, 2010
PubMed
Summary
This summary is machine-generated.

We developed a novel positive feedback circuit for synthetic gene circuits. This genetic amplifier enhances sensitivity and expression levels, offering a modular component for complex biological designs.

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Area of Science:

  • Synthetic Biology
  • Genetic Engineering
  • Systems Biology

Background:

  • Positive feedback is crucial for gene circuit regulation, enabling signal amplification, binary outputs, and hysteresis.
  • Electrical amplifier design principles can inform synthetic gene circuit development for applications like cell-based sensors.

Purpose of the Study:

  • To engineer a modular positive feedback circuit for amplifying genetic signals.
  • To enhance sensitivity and maximum expression levels in synthetic gene circuits without external cofactors.

Main Methods:

  • Developed a constitutively active, autoinducer-independent LuxR variant for the positive feedback module.
  • Experimentally integrated the positive feedback module with tetracycline and aspartate sensor systems.

Main Results:

  • The positive feedback module successfully amplified responses to both tetracycline and aspartate inducers.
  • Demonstrated increased dynamic range and sensitivity in sensor outputs.
  • The circuit functions as a genetic signal amplifier without requiring external cofactors.

Conclusions:

  • The single-gene feedback mechanism is simple and requires no additional modulation.
  • The circuit can amplify diverse transcriptional signals, independent of specific inducers.
  • Its modular nature allows for integration into more complex synthetic gene circuit designs.