Applications

Intrinsic Fluorescence Imaging

Application 1: Protein intrinsic Fluorescence for Crystal Detection or distinguishing Protein Crystals from Salt Crystals

Example 1: Protein crystals among ammonium sulfate crystals

Ammonium sulfate crystals illuminated with white light (left) and UV-light (right). The crystal structure of ammonium sulfate is orthorhombic and therefore it shows a distinct birefringence when illuminated with polarized white light. Whereas, when those crystals are illuminated with UV-light they become invisible, they completely merged with the background.

Example 2: Pure salt crystals:

 
Crystals of ammonium sulfate

Example 3: Crystal screening results:

A: Protein crystals (Diameter ~0.2 mm)
 
 
B: Protein crystals (Diameter ~0.1 mm)
 
 
C: Protein crystal in oily phase (Diameter ~0.3 mm)
 

 

Application 2: RNA and Aptamer Identidication applying the Nucleic Acid specific Dye "SYBR-GOLD":

Example 1: Distinguishing RNA from Salt:

In this example, an RNA-hexamer was crystallized with sodium cacodylate as precipitant. Later, under white light illumination two crystals (A, B) became visible in the drop (left). After addition of SYBER-GOLD to the drop and illumination with UV-light, crystal "A" could be identified as a salt crystal (sodium cacodylate) and crystal "B" as crystals of the RNA-hexamer. 

Example 2: Aptamer-RNA Complex Identification:

Identification of included RNA inside of an Apdamer: White light illumination showed a crystal after screening. In UV-light, the crystal showed intrinsic blue fluorescence and therefore it could be identified as proteinogenic. After addition of SYBR-GOLD to the drop and illumination again with UV-light, the crystal showed green fluorescence, indicating incorporated RNA in the crystal.

 

Trace Fluorescence Imaging

Trace Labeling Procedure

Example: Sample in green light

A10C-1

A11B-1

In situ Dynamic Light Scattering

In Situ DLS Applications

Dynamic Light Scattering
  • Angle Depending
  • Temperature Depending
  • Classic DLS

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a)

Monodisperse sample

b)

Highly oligomerized sample

c)

Partially aggregated sample

Cryo EM Applications

Workflow

A)Protein Purification: After purification, a sample might not be in the desired aggregation state or a biological relevant complex of molecules has not formed yet. Some buffer conditions might support complex formation apart from its natural environment but often such conditions are unknown.

B)Condition Screening: One strategy to obtain biological complexes is the application of various conditions (e.g. sparse matrices) systematically to a sample by adding corresponding buffers. However, a manual pipetting procedure is a tedious task and errors are likely. In order to even the workflow, automated dispensing systems (like the Oryx8) are available enabling a time, material and manpower efficient way to apply such buffer matrices. Usually, standard microbatch plates and samples sealed under inert paraffin oil are used.

C)Sample Qualification: However such an approach results in many conditions (usually 96) exceeding grid holding capacities of most grid carriers by far. Furthermore, most of the applied conditions have a negative effect on the sample, leading to a very inefficient usage of a cryo-EM when all samples would be transferred to grids and investigated by cryo-EM. A key technology to select samples for subsequent cryo-EM analysis is in situ DLS (performed with the SpectroLight 600). It allows to identify suitable buffer conditions by particle size determination, non-invasively and directly in wells of a microbatch plate. Size and dispersity determination enables identification of the few conditions that stabilizes the desired macromolecular complex.

D)Sample Transfer: The few good conditions can be selected for subsequently investigation for cryo-EM, resulting in a significant increase of positive hits on the grids.