smb325-LOG Page Fall 2010

Created page smb325 - 9/23/2010
Investigating a-tocopherol (Vitamin E) compound
Set up VPN to access Drexel databases on my laptop in class

Changing topic smb325 - 9/30/2010
Changing research topic to cholesterol because of lack of readily available information on a-tocopherol acetate

Find 5 independent sources of 5 properties associated with a molecule of your choice smb325 - 11/11/2010

Alfa Aesar Website Link MSDS

Melting Point (MP): 148-150 C
Decomposition Temperature (DT): 360 C
Density (D): 1.067 g/cm^3 @ 20 C
Solubility (S): 12.9 g/L @ 20 C in Benzene

Hawley's Condensed Chemical Dictionary (15th Ed.) p. 295

MP: 148.5 C
DT: 360 C
D: 1.067 g/cm^3 @ 20 C

From Knovel per Merck Index Row Number 3674 Link

Molecular Weight (MW): 386.65 g/mol
MP: 148.5 C
D: 1.052 g/cm^3 (anhydrous)

National Library of Medicine Toxnet Link

MP: 148.5C
DT: 360C
Sol: 0.095 mg/l @ 30 C in H2O

Sigma-Aldrich Link MSDS 1 MSDS 2

MP: 147-149 C
DT: 360 C
D: 1.067 g/cm^3
MW: 386.65 g/mol

JT Baker Link

DT: 360 C
D: 1.03 g/cm^3
MW: 386.66 g/mol

Santa Cruz Biotechnology Link MSDS

MW: 386.78 g/mol

Acros Organics Link

S: 1 g/2.8 mL (0.357 mg/mL) in ether

Wikipedia Link

S: 0.095 mg/L @ 30 C in H20

Write a summary of one of the articles you are reading for your project paragraph by paragraph

Lipid rafts, cholesterol, and the brain

Cholesterol is thought to be the key bonding agent that holds together lipid rafts, newly theorized (as of 1997) as the key agents in membrane trafficking. Trafficking segregates the membrane of a small organism or cell by the function which occurs at specific sites, be it exo-/endocytosis, cell migration, or phagocytosis. They bury into the lipid bilayer and attract the specific proteins neccessary to facilitate the on-site activity.

The brain contains one quarter of all cholesterol in the human body, specifically to aid in the transmission of neurotransmitters via rafts, and lipid rafts have further influence on axon guidance and neuron signaling. Thus, cholesterol is critical in the role of conducting ions.

This paper also describes the identification of lipid rafts and suggests what effects may come of a deprivation of cholesterol in the brain.

A portion of membrane seen to resist a detergent was found to contain an abundance of certain identifying lipids and cholesterol. All methods of raft identification and isolation show cholesterol and sphingolipids as identifiers,whether or not proteins also associate with the lipids.

The tight packing of the lipids in regions of the membrane evoke the features of liquid ordered domains and even appear in the gel state with further compression. They allow for easy manipulation in the lab so that researchers can view the effects of cholesterol on domain formation.

As cholesterol is removed from the site, the lipid rafts lose proteins due to a decrease in resistance to detergent. Thus, it would appear that to deprive rafts of cholesterol would mean they would quickly dissipate.

Due to the fact that current testing is done with stationary specimens and that rafts in living cells are difficult to view, the current methods don't appear to give consistently valid results.

If a specific fluorescent indicator shows up in these small domains, it means that donor and acceptor indicator molecules are closely packed together, suggesting that the raft is shaping diffusion.

The indicator will diffuse randomly through the domain when unguided by rafts, thus removing the fluorescence from the previous example because the donor and acceptor are separated by erratic diffusion.

The test appears to be more valid because the fluorescence will cluster together in the presence of ordered diffusion. Stray observations of fluorescence merely suggest individual donors and acceptors have come within close proximity only by chance.

As discovered in vitro, liquid-ordered protein domains form based on their affinity for lipid rafts, but liposome domains do not form in the presence of lipid rafts. Another theory suggests that raft molecules surround raft proteins, and another theory suggests underlying cell functions regulate domain formation.

Cholesterol plays a part in domain formation, but also makes cell membranes more pliable while also growing thicker. This can positively influence the association of proteins with rafts. Thus, the metering of cholesterol in the raft environment can inhibit and promote cell signaling. Cell signaling and signal transit being core to brain function, cholesterol must therefore always be present in the brain but closely regulated.


[Full Marks JCB]