Johan Engelbrektsson

Biogenic Amines in Microdissected Brain Regions of Drosophila melanogaster Measured with Micellar Electrokinetic Capillary Chromatography—Electrochemical Detection

Micellar electrokinetic chromatography with electrochemical detection has been used to quantify biogenic amines in microdissected Drosophila melanogaster brains and brain regions. The effects of pigment from the relatively large fly eyes on the separation have been examined to find that the red pigment from the compound eye masks much of the signal from biogenic amines. The brains of white mutant flies, which have characteristically low pigment in the eyes, have a significantly simplified separation profile in comparison to the red-eyed, wild-type, Canton S fly. Yet, the white mutant flies were found to have significantly less amounts of dopamine, l-3,4-dihydroxyphenylalanine (L-DOPA), salsolinol, and N-acetyltyramine in their dissected brains when compared to dissected brains of Canton S flies. In addition, significant variation has been observed in the dissected brains between individual flies that might be related to changes in neurotransmitter turnover. The transgenic GFP fly line (TH-GFP), for which the overall profile of biogenic amines is not found to be significantly different from Canton S, can be used to visualize the location of dopamine neurons. Biogenic amines were then quantified in three brain regions observed to have dopamine levels, the central brain, optic lobes, and posterior superiormedial protocerebrum (PPM1) region.

Steady-state electrochemical determination of lipidic nanotube diameter utilizing an artificial cell model.

By exploiting the capabilities of steady-state electrochemical measurements, we have measured the inner diameter of a lipid nanotube using Ficks first law of diffusion in conjunction with an imposed linear concentration gradient of electroactive molecules over the length of the nanotube. Ficks law has been used in this way to provide a direct relationship between the nanotube diameter and the measurable experimental parameters Deltai (change in current) and nanotube length. Catechol was used to determine the Deltai attributed to its flux out of the nanotube. Comparing the nanotube diameter as a function of nanotube length revealed that membrane elastic energy was playing an important role in determining the size of the nanotube and was different when the tube was connected to either end of two vesicles or to a vesicle on one end and a pipet tip on the other. We assume that repulsive interaction between neck regions can be used to explain the trends observed. This theoretical approach based on elastic energy considerations provides a qualitative description consistent with experimental data.

Steady-State Electrochemical Determination of Lipidic Nanotube Diameter Utilizing An Artificial Cell Model

By exploiting the capabilities of steady-state electrochemical measurements, we have measured the inner diameter of a lipid nanotube using Ficks first law of diffusion in conjunction with an imposed linear concentration gradient of electroactive molecules over the length of the nanotube. Ficks law has been used in this way to provide a direct relationship between the nanotube diameter and the measurable experimental parameters change in current and nanotube length. Catechol was used to determine the change in current attributed to its flux out of the nanotube.Comparing the nanotube diameter as a function of nanotube length revealed that membrane elastic energy was playing an important role in determining the size of the nanotube and was different when the tube was connected to either end of two vesicles or to a vesicle on one end and a pipette tip on the other. We assume that repulsive interaction between neck regions can be used to explain the trends observed. This theoretical approach based on elastic energy considerations provides a qualitative description consistent with experimental data.