How much His tagged protein can 1g Ni NTA filler bind to?

For a 1 g small package, if there is domestic stock, domestic products generally take 3–7 days, while imported products commonly take 1–2 weeks; however, if there is no stock or cold chain/customs clearance is involved, it may be extended to 3–4 weeks. For this specification, I recommend prioritizing original manufacturer small packages or prepacked column alternatives that are in stock domestically, rather than looking only at the unit price: 1 g of resin also requires empty columns, desalting/regeneration reagents, and the overall cost may not necessarily be low. If you are only doing three or four small-scale runs, a 5 mL prepacked gravity column is often more convenient than 1 g of dry powder, with a fixed bed volume and better reproducibility. When purchasing, confirm the resin storage conditions (4°C or room temperature), whether it can be shipped at room temperature, and whether loading capacity references are provided, to avoid buying aliquoted product without a COA.

The difference in stability between domestic and imported 1g small packaging batches is mainly reflected in three aspects: particle size uniformity, Ni ion detachment rate, and whether the storage solution is standardized. Imported mainstream brands usually have a relatively complete COA for each batch, and the fluctuation of column bed volume/load is relatively small; Sometimes, there may be differences in column bed volume after dry powder rehydration in domestic packaging or small factories, and it is necessary to calibrate the loading capacity by oneself. It is recommended to wash with low concentration EDTA before reloading Ni, regardless of the brand, and conduct a loading test with the same batch of His protein upon receipt. If the 1g specification is not sealed by the original factory but packaged by an agent, the probability of yellowing, clumping, or leakage will increase. Please check upon arrival.

After lysis of 200 mL bacterial culture, typically 10–30 mL of soluble supernatant is obtained, and the protein amount may range from less than 1 mg to several tens of mg. To determine whether 1 g is sufficient, do not look only at the number of uses; calculate based on "expected target protein amount/total resin binding capacity." For small-scale purification three to four times, if the target protein is 2–5 mg each time, 1 g can support it; if a single run exceeds 10 mg, it is recommended to directly purchase a 5 mL prepacked column or 2–3 g of resin. Another commonly overlooked point is Ni resin reuse: as long as regeneration and Ni stripping/loading are done properly, a 1 g specification can be recovered for multiple uses in purification of the same protein, but the binding capacity will decrease progressively with each use.

After rehydration of 1g Ni NTA agarose dry powder, about 3-4 mL of homogenate can usually be obtained. After sedimentation, the column bed volume is approximately in the range of 2-4 mL. Small scale gravity columns are usually filled with 1-2 mL of homogenate. According to the conventional Ni NTA/IDA system, combined with empirical values of loading, the column bed is mostly between 10-30 mg/mL, depending on the degree of His tag exposure, protein molecular weight, flow rate, and competition with impurities. So the total amount of 1g specification is roughly in the tens of mg range. If the target protein is soluble and highly expressed in 200 mL of bacterial solution, several mg to over ten mg can be obtained in one or two batches, and small-scale purification of 1g in three or four batches is relatively tight but feasible; If the expression is very low, it is necessary to optimize the expression or add fillers first.