Related Experiment Video
Updated: Feb 8, 2026
10:21
Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions
Published on: October 5, 2019
9.0K
Photosensitized Membrane Permeabilization Requires Contact-Dependent Reactions between Photosensitizer and Lipids
Isabel O L Bacellar1,2, Maria Cecilia Oliveira3, Lucas S Dantas1
1Departamento de Bioquímica, Instituto de Química , Universidade de São Paulo , Avenida Prof. Lineu Prestes 748 , São Paulo , SP , Brazil , 05508-000.
Journal of the American Chemical Society
|July 11, 2018
Summary
Photosensitizers and light permeabilize lipid membranes via photooxidation. Direct photosensitizer-lipid contact is essential for aldehyde formation, which drives membrane permeabilization and cell death.
Area of Science:
- Biochemistry
- Membrane Biophysics
- Photochemistry
Background:
- Lipid oxidation mechanisms are known, but photosensitizer-mediated membrane permeabilization pathways remain unclear.
- Photosensitizers (PS) and light induce lipid oxidation, affecting membrane integrity.
- Understanding these processes is crucial for photodynamic therapy (PDT) applications.
Purpose of the Study:
- To elucidate the chemical steps of photosensitizer-induced lipid photooxidation.
- To characterize photooxidation products and their impact on lipid bilayers.
- To correlate photosensitizer-lipid interactions with membrane permeabilization and cell-killing efficiency.
Main Methods:
- Utilized phenothiazinium-based photosensitizers (methylene blue, MB, and DO15) with varying lipid colocalization.
- Investigated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and polyunsaturated lipid liposomes.
- Quantified lipid oxidation products (hydroperoxides, alcohols, ketones, aldehydes) using analytical techniques.
Main Results:
- DO15, with higher lipid colocalization, permeabilized membranes significantly more than MB.
- Lipid aldehydes were identified as key products linked to membrane permeabilization.
- Direct photosensitizer-lipid contact promoted the formation of oxidized products, particularly aldehydes.
Conclusions:
- Direct photosensitizer-lipid interactions are critical for efficient lipid oxidation and aldehyde generation.
- Aldehyde formation significantly lowers the energy barrier for water permeation across membranes.
- Membrane binding affinity of photosensitizers directly correlates with their cell-killing efficacy in PDT.
Related Concept Videos
01:19Contact-dependent Signaling
47.6K
Contact-dependent signaling, as the name suggests, requires that communicating cells be in direct contact with each other. This is achieved either through receptor-ligand interactions or by specialized cytoplasmic channels that allow the flow of small molecules between cells. In animal cells, channels called gap junctions facilitate contact-dependent signaling in certain tissues, whereas, plasmodesmata perform a similar function in plants.
Gap Junctions
In animal cells, gap junctions are formed...
Gap Junctions
In animal cells, gap junctions are formed...
47.6K
01:18Lipids: Dietary Sources and Requirements
2.1K
Lipids are an essential component of a balanced human diet. Triglycerides, which make up the majority of dietary lipids, are found in both saturated fats—commonly present in meat, dairy products, and certain tropical plants like coconut, and hydrogenated oils such as margarine and baking shortenings (trans fats)—and unsaturated fats, which are abundant in seeds, nuts, olive oil, and most vegetable oils. The main sources of cholesterol include egg yolks, various meats and organ...
2.1K
02:55Temperature Dependence on Reaction Rate
89.2K
The Collision Theory
Atoms, molecules, or ions must collide before they can react with each other. Atoms must be close together to form chemical bonds. This premise is the basis for a theory that explains many observations regarding chemical kinetics, including factors affecting reaction rates.
The collision theory is based on the postulates that (i) the reaction rate is proportional to the rate of reactant collisions, (ii) the reacting species collide in an orientation allowing contact between...
Atoms, molecules, or ions must collide before they can react with each other. Atoms must be close together to form chemical bonds. This premise is the basis for a theory that explains many observations regarding chemical kinetics, including factors affecting reaction rates.
The collision theory is based on the postulates that (i) the reaction rate is proportional to the rate of reactant collisions, (ii) the reacting species collide in an orientation allowing contact between...
89.2K
01:32Membrane Lipids
34.3K
Lipids are an essential component of all biological membranes. The average lipid content in mammalian membranes is 50%, though it can be as low as 20% in the inner mitochondrial membrane or as high as 80% in the myelin sheath present around the nerve cells.
Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and sphingomyelin are the most common phospholipids present in mammalian membranes. At physiological pH, phosphatidylserine is negatively charged, while the other three...
Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and sphingomyelin are the most common phospholipids present in mammalian membranes. At physiological pH, phosphatidylserine is negatively charged, while the other three...
34.3K
01:16Cycloaddition Reactions: MO Requirements for Thermal Activation
4.6K
Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.
4.6K
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
2.7K
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
2.7K