[3dem] reflections from gold fiducials

Lars-Anders Carlson lars-anders.carlson at umu.se
Mon Nov 6 15:45:38 PST 2017


Hi all,
Thanks for the input. If I try to summarise:
1. They're Bragg reflections. (I completely agree!)
2. Several people have seen this. (Thanks for providing me with the 3dem 
equivalent of the therapist's "you're not alone"!).

I guess my main surprise when I saw the reflexes was that I actually 
haven't seen this more often, in spite of years of imaging with gold 
fiducials +/-FEG/OA/defocus/etc. I guess - as others appear to agree 
with - that the level of mosiaicity varies.

Best wishes and thanks to all,
Lars



On 2017-11-06 23:42, Jaap Brink wrote:
> Hi,
> 
> These are bright-field reflections arising from Bragg diffraction of the 
> gold lattice in the nanogold. They should disappear at exact or Gaussian 
> focus. But, you don't want to do that. The way to remove them should be 
> to dial in a smaller OL aperture that cuts off everything beyond 3Å 
> resolution.
> 
> Jaap
> ----
> Jacob Brink Ph.D.
> TEM Product Manager Life Sciences
> JEOL USA, Inc., Peabody MA 01960
> (978) 317-9561
> 
> Sent from mobile device. Please excuse typos and this reply's brevity as 
> I'm using all thumbs to type :-)
> 
> On Nov 6, 2017, at 4:18 PM, "vojta at strubi.ox.ac.uk 
> <mailto:vojta at strubi.ox.ac.uk>" <vojta at strubi.ox.ac.uk 
> <mailto:vojta at strubi.ox.ac.uk>> wrote:
> 
>> Hi Lars,
>>
>> To my knowledge coloidal gold particles are almost always 
>> polycrystalline.  At higher magnifications you will start to see lines 
>> corresponding to different spacing of the crystal lattices and if you 
>> crank the magnification all the way up to something like 0.3 Apix you 
>> can see individual columns of atoms (attached below is an image of a 
>> wurtzite crystal I took on an F30 some time ago).  The reflections you 
>> see move closer to each gold bead as you get nearer to focus which I 
>> think is an amazing example of high resolution information being 
>> delocalised with defocus.
>>
>> Only rarely do we see reflections like these in tomograms, I would 
>> also like to know what dethermines if they show up or not!
>>
>> If you're interested in this topic I strongly recommend watching the 
>> supplemental videos in Lu et al. (2010, 
>> https://www.nature.com/articles/nnano.2010.4) and you can also find 
>> plenty of publications on the structure of gold nanoparticles.
>>
>> Best,
>>
>> Vojta
>>
>> Vojtěch Pražák
>> Graduate Student
>> Department of Structural Biology
>> The Wellcome Trust Centre for Human Genetics
>> Roosevelt Drive, Oxford, OX3 7BN UK
>> University of Oxford
>>
>> Email: vojta at strubi.ox.ac.uk <mailto:vojta at strubi.ox.ac.uk>
>> Web: https://www.strubi.ox.ac.uk/research/kay-grunewald
>>
>>
>> ---- Original message ----
>>> Date: Mon, 6 Nov 2017 21:13:14 -0000
>>> From: "3dem" <3dem-bounces at ncmir.ucsd.edu 
>>> <mailto:3dem-bounces at ncmir.ucsd.edu>> (on behalf of "Lars-Anders 
>>> Carlson" <lars-anders.carlson at umu.se 
>>> <mailto:lars-anders.carlson at umu.se>>)
>>> Subject: [3dem] reflections from gold fiducials
>>> To: <3dem at ncmir.ucsd.edu <mailto:3dem at ncmir.ucsd.edu>>
>>>
>>> Dear community,
>>> We encountered something during tilt series acquisition recently that I
>>> hadn't seen before: several 10 nm gold fiducials gave clear reflections,
>>> see attached image (compressed snapshot - it looks stronger in the
>>> original images).
>>>
>>> The reflections were often symmetrically arranged around a fiducial and
>>> would then disappear at the next tilt ange. We used a 100 um objective
>>> aperture at a Krios at 300kV. Admittedly I never worried about the
>>> crystalline arrangement of gold fiducials before, so I took some higher
>>> mag images of the fiducials, and some of them look mosaic, others more
>>> monocrystalline (see image), which could explain why some cause more
>>> reflections than others.
>>>
>>> Is this something people have encountered before? Are some batches of
>>> fiducials better ordered than others at the atomic level? I'm curious to
>>> hear what people think of this since it fascinated me...
>>>
>>> Cheers,
>>> Lars
>>>
>>> -- 
>>> Lars-Anders Carlson
>>> Assistant Professor
>>> Dept of Medical Biochemistry and Biophysics
>>> Wallenberg Centre for Molecular Medicine
>>> Umeå University
>>> 901 87 Umeå, Sweden
>>>
>>> lab website including OPEN POSITIONS:
>>> http://www.carlsonlab.se/
>>> ________________
>>> gold2.jpg (187k bytes)
>>> ________________
>>> _______________________________________________
>>> 3dem mailing list
>>> 3dem at ncmir.ucsd.edu <mailto:3dem at ncmir.ucsd.edu>
>>> https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem
>> <Photo 01-06-2017, 16 50 14 (1).jpg>
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-- 
Lars-Anders Carlson
Assistant Professor
Dept of Medical Biochemistry and Biophysics
Wallenberg Centre for Molecular Medicine
Umeå University
901 87 Umeå, Sweden

lab website including OPEN POSITIONS:
http://www.carlsonlab.se/


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