Basic guidelines on using upper case versus lower case in scientific writing
Overusing capital letters is a more common error in scientific writing than the other way around, that is, not using them where they are required. Capitalization is certainly a problem that confronts writers and editors, and the space devoted to capitalization by many style guides is one indication of how common the problem is: New Hart’s Rules1, Scientific Style and Format2, and AMA Manual of Style3 each devotes a whole chapter to it.
Although it is impossible to offer categorical advice for every case, some general principles apply to most cases. One overarching principle is to use lowercase letters as default and to use capitals only when you must (as, for example, with proper nouns and at the beginning of each sentence). As New Hart’s Rules [1, p. 96] puts it: “Overuse of initial capitals is obtrusive, and can even confuse by suggesting false distinctions.”
Frequently, the matter can be resolved by sticking to the style used by a given journal: for instance, some journals use the so-called ‘headline style’ (or title case) for headings. Accordingly, if your target journal uses the headline style and prints ‘Materials and Methods’ instead of ‘Materials and methods’ (note the lowercase m in ‘methods’), use that style.
In the same way, observe the style used by the journal in references and follow that style: some journals use the title case for titles of journals and books; some don’t (Annals of Applied Biology versus Annals of applied biology and Principles of Organic Chemistry versus Principles of organic chemistry).
When using abbreviations, it is useful to remember that just because an abbreviation is written in capitals does not mean that the capitalization must be retained when the abbreviation is set out in full: for example, EMF but electromagnetic field (the m and the f are lowercase), PCB but printed circuit board, and WAIS but wide area information service.
There is another criterion to use in choosing between capitals and lowercase in abbreviating and enumerating specific instances of such words as chapter, figure, and page: checking whether the enumeration is deliberate or accidental: Chapter 2 or Figure 5, but page (or p.) 7 and column (or c.) 2, because page numbers and column numbers are a function of page layout and can change; whereas the division of text into chapters and the choice of figures are deliberate choices.
 OUP. 2014. New Hart’s Rules: the Oxford style guide, 2nd edn. Oxford: Oxford University Press. 464 pp.
 CSE , Style Manual Committee. 2014. Scientific Style and Format: the CSE manual for authors, editors, and publishers, 8th edn. Wheat Ridge, Colorado, USA: Council of Science Editors. 722 pp.
 AMA. 2007. AMA Manual of Style: a guide for authors and editors, 10th edn. New York: Oxford University Press [and American Medical Association]. 1010 pp.