AFM Measurements of DNA
Figure 2: AFM image of gold nanoparticles bound from below to the double- stranded DNA [1].
transport through the strand. Similarly, bases which are electron-rich have better electron conductivity than those which have fewer available electrons [Figure 3]. Tis is not solely academic; electronic behavior of DNA is very closely related to function. Tere are electrochemical processes, which are mediated by these DNA biological molecules. For instance, radiation damage, and mutation—how does the DNA deal with an extra electron or an absence of an electron located somewhere along its chain?” [3] Te characteristics of electron conductivity in DNA also
have implications in molecular electronics, which is trying to achieve devices that, instead of working on the standard silicon circuitry, function through innocuous molecules. Because of DNA’s facility to bind with similar types of DNA molecules, it is not necessary to physically place each molecule in a set location. DNA put into solution can be expected to organize itself in the right way and become a predictable medium for electrons.
Vibration Isolation Critical to DNA Research Te Weizmann Institute
is one of the few research groups in the world that has actually managed to measure the electrical transport pro- perties of a single molecule of DNA. One of the chal- lenges that presents itself in nanoscale research is
22
Figure 3: Current versus voltage curves for DNA strands with different concen- trations of the guanine-cytosine (GC) base pair, which releases electrons more readily than the thymine-adenine (AT) base pairs. Higher numbers of GC pairs are increasingly electron rich.
vibration isolation. Every laboratory measuring and imaging at the nano-level is dealing with problems of site vibration, which compromises to a greater or lesser degree the imaging quality and data sets that are acquired through ultra-high-resolution microscopy. A critical factor in the Weizmann Institute’s ability to consistently measure DNA electron structures at such extreme nano-level resolutions is the lab’s use of negative-stiffness vibration isolation systems (Minus K Technology) which produced the ultra-stable environment that the AFMs needed to execute this research [4, 5]. “Any lab site is subject to vibrations from machines, vibrations of the building itself, and even from people walking
Figure 4: Schematic of a negative-stiffness vibration isolator.
www.microscopy-today.com • 2010 September
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76