The most popular method for purification of proteins and charged molecules is called Ion exchange chromatography. Conversely, in anion exchange chromatography, negatively charged molecules are attracted to a positively charged solid support. In cation exchange chromatography positively charged molecules are attracted to a negatively charged solid support. A journal is a periodical publication intended to further progress of science, usually by reporting new research. Most journals are highly specialized, although some of the oldest journals publish articles, reviews, editorials, short communications, letters, and scientific papers across a wide range of scientific fields. Journals contain articles that peer reviewed, in an attempt to ensure that articles meet the journal's standards of quality, and scientific validity. Each such journal article becomes part of the permanent scientific record.