Abstract: There are provided a cell aggregate that can be used as a cell preparation in regenerative medicine, maintains the original characteristics of cells, and has high safety, and a method for simply and safely maintaining the cell aggregate size, the cell characteristics and viability suitable for use as a cell preparation in regenerative medicine. According to an aspect of the present invention, a cell aggregate maintaining method is a method including a maintenance process of maintaining a liquid containing a plurality of the cell aggregates at a temperature which is lower than a culture temperature of the cells and at which the liquid is not frozen.

Abstract: A process for preparing a purified refolded monomer or dimer of a bone-derived factor, which comprises subjecting an inclusion body of a bone-derived factor produced by genetic engineering to the following steps a) to c) in sequence: a) introducing a polynucleotide encoding a bone morphogenetic factor into a bacterium, expressing said bone morphogenetic factor in the form of an inclusion body, recovering said inclusion body and treating it with a denaturing agent to obtain a solubilized monomer, b) treating the solubilized monomer without purification directly with a refolding solution to obtain a refolded monomeric bone morphogenetic factor, c) subjecting the refolded monomeric bone morphogenetic factor to purification.

Abstract: A process for preparing a purified refolded monomer or dimer of a bone-derived factor, which comprises subjecting an inclusion body of a bone-derived factor produced by genetic engineering to the following steps a) to c) in sequence: a) introducing a polynucleotide encoding a bone morphogenetic factor into a bacterium, expressing said bone morphogenetic factor in the form of an inclusion body, recovering said inclusion body and treating it with a denaturing agent to obtain a solubilized monomer, b) treating the solubilized monomer without purification directly with a refolding solution to obtain a refolded monomeric bone morphogenetic factor, c) subjecting the refolded monomeric bone morphogenetic factor to purification.

Abstract: A process for preparing a purified refolded monomer or dimer of a bone-derived factor, which comprises subjecting an inclusion body of a bone-derived factor produced by genetic engineering to the following steps a) to c) in sequence:

Abstract: E. coli deficient in protease activities, said activities being not inhibited with diisopropyl fluorophosphate, phenylmethylsulfonyl fluoride, N-.alpha.-tosyl-L-lysyl chloromethyl ketone, N-tosyl-L-phenylalanine chloromethyl ketone, ethylenediamine tetra-acetic acid, leupeptin, antipain, .alpha..sub.2 -macroglobulin or chymostatin, and being inhibited with zinc chloride or copper chloride is disclosed.This E. coli is useful as a host for creating a transformant capable of expressing an exogenous protein or polypeptide.The protein or polypeptide expressed by the transformant may be extracted and purified with a quite low level of decomposition.

Abstract: A method of purifying a polypeptide having a physiological activity such as one having interferon activities from a culture mixture of a microorganism obtained by a recombinant DNA technique and capable of producing the polypeptide is disclosed. The method comprises subjecting the cultured cells to extraction and purification in the presence of a salt of zinc or copper and polyethyleneimine thereby inhibiting decomposition and denaturation of the polypeptide. The extracted polypeptide can be further purified by column chromatographies using a column containing an anion exchange resin, column containing a cation exchange resin and column containing a gel filtration resin.