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Benjamin Franklin was born
He was born in Boston, United States.
("Scientific Exploits of Ben Franklin Part 1: The Oil Drop Experiments"). -
Benjamin Franklin: The Oil Drops Experiment
He observed that a specific amount of oil covered a set area of pond water. More oil would cover a greater area. Franklin concluded that there was a limit to how thin the oil could be spread over a surface. ("Scientific Exploits of Ben Franklin Part 1: The Oil Drop Experiments"). -
Benjamin Franklin: The Oil Drops Experiment contd. ("Scientific Exploits of Ben Franklin Part 1: The Oil Drop Experiments").
Franklin began to pour olive oil in a pond near Clapham Common. He observed that even on a windy day, a teaspoon of oil would spread across the surface of the water and calm the waters, leaving the surface "as smooth as a looking glass". He poured the same amount of oil on a marble table or piece of glass and observed that it did not spread. He concluded that there must've been a special interaction between water and oil molecules. -
Benjamin Franklin died
Benjamin Franklin died in Pennsylvania, United States.
("Scientific Exploits of Ben Franklin Part 1: The Oil Drop Experiments"). -
Thomas Young's inspiration
Thomas Young, a professor at the Royal Institution, inspired Lord Rayleigh with his work on measuring the size of molecules, specifically water, and the surface tension in liquids.
("The Editors of Encyclopædia Britannica"). -
Lord Rayleigh was born
Lord Rayleigh was born in Essex, England. His original name was John William Strutt.
(Masters). -
Wilhelm Pfeffer was born
Wilhelm Pfeffer was born in Grebenstein, Germany.
("Pfeffer, Wilhelm Friedrich Philipp"). -
Agnes Pockels was born
Agnes Pockels was born in Venice, Italy.
("Agnes Pockels - Housewife and Chemist"). -
Wilhelm Pfeffer ("Pfeffer, Wilhelm Friedrich Philipp").
Pfeffer researched osmosis with Trauble's artifical cell membranes. Trying to mimic the extremely high osmotic pressures found in plant cells, he found them Trauble's membranes to be too weak as they burst under pressure. Pfeffer then tried to invent his own, creating Pfeffer Zelle. By adding ferrocyanide to them, the walls withstood higher pressures and Pfeffer was able to calculate solutions and their solubility at specific temperatures. He proposed this model as a plant cell membrane. -
Charles Ernest Overton was born
Charles Ernest Overton was born was born in Chestshire, England. ("Overton, Charles Ernest"). -
Moritz Traube
Mortiz Traube hypothesized that a semi-permeable barrier existed between the interior and exterior of the cell. He created artificial semi permeable membranes and used them to study osmosis and diffusion.
("Cell Membrane"). -
Irving Langmuir was born
Irving Langmuir was born in Brooklyn, New York.
("Surface chemistry advances have come with collaboration and, even, gallantry"). -
Agnes Pockels
Agnes Pockels was a housewife with no college education. As a housewife, she was constantly exposed to greasy dish water. This led to her experimenting with soap solution and the surface tension of water. She invented a simple device, consisting of a tin trough with a movable strip of tin on top. She would fill the trough with water contaminated with many things. By moving the mixture, she was able to measure the differences in surface tension with water containing different things. (Masters). -
Agnes Pockels pt2.
Agnes Pockels used her invention to develop a method of clearing the surface of water of the contamintants before a solution of a substance in the solvent appeared on it. The Schieberinne allowed her to make precise measurements of surface thickness and tension.
("Agnes Pockels - Housewife and Chemist"). -
Edmunton Newton Harvey
Edmunton Newton Harvey was born in Philadelphia, Pennsylvania. He became an expert in the area of cell surface studies.
("Edmund Newton Harvey"). -
Lord Rayleigh's Oil Calculations
Lord Rayleigh repeated Franklin's Oil Drop experiment. His work was inspired Thomas Young, a professor at the Royal Institution. By using his extensive knowledge in physics and optics, he was able to calculate the thickness of the oil on the surface of the water to be 16 x 10-8 cm. This is known as the first experimental measurement on molecular dimensions. Due to his numerous other discoveries, like the discovery of the element argon, Rayleigh's calculations were noticed by few.
(Masters). -
Agnes Pockel's Letter (Masters).
After reading about Lord Rayleigh's publications on surface tension, Agnes Pockel sent a 12 page letter to him about her findings. Surprised by her work, Rayleigh sent the letter to the journal Nature, who published it. Afterwards, the physics department at the University of Heidelburg invited her to work in their lab. For the next 40 years, she saw the discovery of surface film and tension advance greatly. Pockel's greatest invention was the Schieberinne, which is still used in chemistry today. -
Agnes Pockels
Pockel recalculated the oil thickness over the surface of water to be 13 x 10-8 cm.
(Masters). -
Charles Overton ("Overton, Charles Ernest").
During this time, it was thought that the cell membrane was impermeable and only water could pass through it. However, Overton became interested in how a cell that was isolated from a solute was still able to take up nutrients and eliminate waste products. He found that non-polar substances readily passed through the cell membrane. He also discovered that there was a correlation in permeation between the substance and their relative fat solubility, its fat and water composition. -
Charles Ernest Overton contd.
The less its fat solubility, the harder it was for the cell to take in the substance. Overton used protoplasts, living plant or bacteria cells with their cell walls removed. Basing his findings off of Pfeffer's previous theory, Overton assumed that an invisible plasma membrane had fat like substances such as cholestrol or phospholipids embedded into its membrane and that certain molecules passed the membrane by dissolving in the lipid component of the membrane. ("Overton, Charles Ernest"). -
Charles Ernest Overton contd. pt2.
This is known as Overton’s lipoid theory of plasma permeability. ("Overton, Charles Ernest"). -
Hugh Davson was born
Hugh Davson was an English physiologist.
("Interacting with the Outside World"). -
James F. Danielli was born
James F. Danielli was a British physical chemist, but majority of his work related to biology. His doctarate research was about the surface properties of lipids. ("Interacting with the Outside World"). -
George Emil Palade was born
George Emil Palade was born in Romania.
("George Palade Biography"). -
Irving Langmuir
Langmuir was an industrial research scientist at General Electric in New York. There, he studied lipids and the interaction of the oil film and water. He proposed that the fatty acid molecules in lipids oriented themselves vertically with the hydrocarbon chains away from the water and the carboxyl group in contact with the surface of the water. This was the key piece in understanding phospholipids in cell membranes.("Surface chemistry advances have come with collaboration and, even, gallantry"). -
Irving Langmuir
Langmuir also improved on Pockel's original apparatus, making it more accurate with measuring surface areas covered in known quantities of oil. The apparatus is known as the Langmuir trough today. (Eichman). -
Lord Rayleigh died
Lord Rayleigh died from a heart attack in Essex, England. (Masters). -
Seymour Jonathan Singer was born
Seymour Jonathan Singer wa born in New York City. (Martin). -
Gorter and Grendel: The Erythrocyte Experiment
By using the known number of cells and the surface area of the erythrocytes, it was discovered that the extracted lipids covered twice the surface area to enclose all the cells. More experiments were conducted with erythrocytes from various sources such as sheeps and rabbits and results showed that the molecule was covered in fatty substances that were two molecules thick. Gorter and Grendel explained this phenomenon as a double layer of lipid surrounding each cell, or a lipid bilayer. (Adams). -
Gorter and Grendel: The Erythrocyte Experiment
Gorter and Grendel used the Langmuir trough and extracted the lipids out of erythrocytes. Erythrocytes were used because they had no membrane bound organelles and no nucleus. Any lipid found would've had to be from the cell membrane. They first extracted the lipids from a known number of erythrocytes. Then, they used the Langmuir trough to determine how large of an area the lipids could cover. (Adams). -
Dr. Albert Claude
Claude created a method called cell fractionation. He grinded cells to break their membranes and sorted the released contents by mass and weight through centrifugation. With this technique, he hoped to separate the functional parts of a cell for a clearer examination with the electron microscope. ("Albert Claude"). -
Danielli and Harvey
Danielli and Harvey worked together in Princeton University. While working in Harvey's lab, Danielli found that proteins were held as a thin film on the outside surface of oil droplets obtained from mackeral eggs. This later attributed to the membrane model proposed by Danielli and Davson. ("Interacting with the Outside World"). -
Danielli and Davson: The First Proposed Membrane Model
Danielli and Davson researched the transportation of substances across the cellular membranes. They believed that proteins that were already in the membrane helped with this transportation. Taking into account Gorter and Grendel's bilayer theory, Danielli and Davson proposed a model that showed a membrane consisting of two lipid layers.The electrically charged head groups faced the aqueous environment both inside and outside the membrane. ("Interacting with the Outside World"). -
Danielli and Davson: The First Proposed Membrane Model
They also believed that there was a continous layer of protein on both sides of the membrane. It was described to be a "sandwich" of lipids. (Eichman). -
J. David Robertson
A layer of protein was later added to both sides of the membrane. Under an electron transmission telescope, a stained membrane was viewed to be "trilaminar". Two darker lines and a lighter inner region was viewed. It was believed that the two darker lines to be two outer dense protein layers separated by the lighter region, the lipid bilayer. He proposed this as the Unit Membrane Concept. ("What are the structure and function of cell membranes"). -
Agnes Pockels died
Agnes Pockels died in Braunschweig, Germany.
("Agnes Pockels - Housewife and Chemist"). -
Garth L. Nicolson was born.
Garth L. Nicolson was born in Los Angeles. (Martin). -
Edmund Newton Harvey died
Edmund Newton Harvey died in Massachusetts, United States. ("Edmund Newton Harvey"). -
George Emil Palade ("George Palade Biography").
George E. Palade researched cellular transport. By using an electron transmission microscope and producing electron micrography, he showed that molecules and ions were engulfed by vesicles that moved to surface of the membrane from within the cell. The vesicle would merge with the outer membrane, engulf the molecule, and then bring the molecule inside the cell. This was a new side of transportation as it was originally thought that substances just passed through the membrane pores of the cell. -
Frye and Ediden
Frye and Ediden supported the theory of proteins being embedded in the cell membrane but hypothesized that the membrane was made up of fluids. They conducted an experiment with a mouse and human cell. Antigens binded to antibodies were tracked. It was observed that over time, the antibodies would spread across the cell, instead of staying in one place. This confirmed Frye and Ediden's hypothesis of the cell membrane being made from fluids and that it did not stay in one place.
(Slim). -
Pliny the Elder
He was the first person to record the effects that oil have on water. He stated "... seawater is made calm by oil, and so divers sprinkle oil on their face because it calms the rough element…”
("Pliny the Elder"). -
S. J. Singer and G. Nicolson (Martin).
Singer and Nicolson demonstrated that water soluble proteins could dissolve in non polar and non aqueous solutions. He also discovered that the shape of a protein differed in hydrophobic and hydrophillic environments. These led him to wonder about the relationship between proteins and the lipid rich and non aqueous environment of a cell membrane. This changed the current Davson-Danielli model at the time, as their model had protein facing aqueous environments on both sides of the membrane. -
S. J. Singer and G. Nicolson
The proteins they obsereved were described as globular and rather than sandwiching phospholipid layers, the proteins were floating within the lipid bilayer. The hydrophillic heads of the phospholipids were facing the aqueous solutions while the hydrophillic tails were faced inward away from the aqueous solution. Proteins spanned across the entire fluid membrane. (Eichman). -
James Danielli died
("Interacting with the Outside World"). -
Unwin and Henderson
The proteins in the fluid membrane were studied by Unwin and Henderson. They discovered that a portion of the proteins were hydrophobic in nature, and bonded to the hydrophobic portion of the phospholipid membrane. The proteins arranged themselves in a three dimensional shape and were found to be in an alpha helix. (Eichman). -
Peter Agre: Membrane Proteins
He called these aquaporin, meaning "water pore".
("Molecular channels through the cell wall"). -
Peter Agre: Membrane Proteins ("Molecular channels through the cell wall").
Agre studied various membrane proteins and observed that there was a selective filter that prevented some ions from passing through the molecular membrane. He believed that these were because of some specific proteins. He tested this hypothesis by placing cells with the protein and cells without the protein in a water solution. The ones with the protein swelled up and the ones without were unaffected. He concluded that the membrane became permeable to water if protein was present. -
Hugh Davson died
("Interacting with the Outside World"). -
Roderick MacKinnon: Ion Channels contd.
The cell could control the opening and closing of the filter through a sensory gate at the bottom of the channel. Certain sensors reacted to certain signals.
("Molecular channels through the cell wall"). -
Roderick MacKinnon: Ion Channels
MacKinnon produced the first high resolution picture of an ion channel called KcsA in the bacteria: Streptomyces lividans. He studied the ion filter that was theorized in the 1970's. He observed that the ion channel permited potassium ions to pass through but not sodium ions. The sodium ion could not fit between the oxygen atoms in the filter and therefore, remained in the water solution. ("Molecular channels through the cell wall").
("Molecular channels through the cell wall"). -
George Emil Palade died
George Emil Palade died in California, United States.
("George Palade Biography"). -
Mary Kraft
Using molecule specific imaging methods, Kraft observed that sphingolipids were found in patches across the cell membrane, rather than concentrated in one area. Also, it was discovered that lipid aggregation still occurred despite a membrane being low on cholestrol. It was originally thought that cholestrol caused the lipid aggregation.
("New look at cell membrane reveals surprising organization"). -
Prof. Dr. Philippe Bastiaens: KRas cancerous proteins (Schmick, Vartak, and et al).
Prof. Dr. Philippe Bastiaens and other scientists at the Max Planck Institute of Molecular Physiology have discovered that the protein KRas can be tracked within the cell and its membrane. The protein can be found inside other membranes within the cell as well as at surface of the cell membrane. This discovery is crucial because KRas has been found to be a factor in several types of cancer. By tracking KRas, scientists can better understand and develop anti-cancer drugs like deltarasin.
