Table 1.
Summary of sample delivery methods currently being deployed for SFX.
| Sample Delivery Method | Average Flow Rate | Advantages | Limitations | Experimental Environment | Examples of Systems/Proteins Studied |
|---|---|---|---|---|---|
| Gas Dynamic Virtual Nozzle91 | 10-25 μL/min67 | amenable for TR-SFX1,54, compatible with most systems | high sample consumption3,11,48, freezing around nozzle tip48, fragile crystals might be damaged during jetting83,92, requires crystals to be filtered107 | vacuum | photosystem I & II1,99, photosystem I-ferredoxin54, lysozyme5, cathepsin B6, photosynthetic reaction center4, Cry3A14, photoactive yellow protein20, P-type ATPase22, myoglobin34, phycocyanin29, B subunit of cholera toxin-membrane-proximal region of gp41100, CPV17 polyhedrin15, trans-acting acyl transferase68, RNA polymerase B II68, parathyroid hormone receptor l83 |
| Electrospinning47 | 140-3100 nL/min47 | low sample consumption47, compatible with membrane proteins 101 | requires cryoprotectant to prevent the jet from freezing47, unknown if high electric fields affect crystals25 | vacuum | photosystem II101, 30S ribosomal subunit92, thermolysin102 |
| Lipidic Cubic Phase11 | 50-200 nL/min8 | low sample consumption8, crystals grown in LCP do not need to be harvested8, some soluble crystals post-crystallization can be mixed to conserve sample29 | Debye Sherrer rings25, membrane protein crystals cannot be mixed post crystallization25, crystals grown in LCP cannot be filtered before injection | both | 5-HT2B receptor8, smoothened receptor11, human delta opioid receptor10, human angiotensin receptor24, rhodopsin arrestin complex30, diacylglycerol kinase17, lysozyme29, phycocyanin29 |
| Grease3 | 460-480 nL/min3 | low sample consumption3 | Debye-Sherrer rings25, not shown to be compatible with membrane proteins25 | atmosphere | lysozyme3, glucose isomerase3, thaumatin3, fatty acid–binding protein type 33, luciferin-regenerating enzyme27 |
| Agarose25 | 100-200 nL/min25 | low sample consumption25, compatible with membrane and soluble proteins25, low background25 | requires cryoprotectant to prevent the jet from freezing when operated in vacuum25 | both | phycocyanin25, photosystem I & II25, sindbis virus69 |
| fixed target: sample supports (wafers57,103,104 and chips105,106) | NA | low sample consumption105, compatible with 2D crystals103, target can be rotated about a fixed angle105 | commercial wafers/chips material is not X-ray transparent104,105, low data collection rates (<10 hz, limited by velocity of sample holder)57, crystal traps can produce crystal orientation biases105 and fill rate is limited to ~50% to prevent crystal stacking106, in vacuum experiments requires emerging crystals in oil57,104, unless crystals are grown on a chip they must be transferred105,106 | both | rapid encystment protein 24 kDa57, bacteriorhodopsin103, anthrax toxin protective antigen104, lysozyme105, sperm whale myoglobin106 |
| Fixed Target: Goniometer107(Grids/Mesh/Loops) | NA | amenable to micro- and to macro- crystals107, compatible with standard goniometers107 | requires cryopreservation and freezing107, not amenable for TR-SFX, requires hitting the crystal in a different position each shot to avoid damage | atmosphere | RNA polymerase II107, general transcription factor IIB107, large nucleic acid scaffold107, monomeric iron-containing hydrogenase 107, sperm whale myoglobin107, cytochrome c oxidase108, synaptotagmin-1 SNARE complex109, β2-adrenoreceptor/nanobody complex107, cyclophilin A110 |