<p>Supposed if I have 2yrs of research experience, good LOR, 2nd upper hons, would having a co-authored publication in PNAS be a big help? We all know that co-author probably do a small part in the whole project but wondering would this be favourable to my application for grad school?</p>
<p>Of course it will be of considerable help. First author is much more impressive but I really don’t think that’s expected of you prior to grad school (which is not to say that you won’t be competing against some people with such publications). It shows that you are aware of the importance of publication and stands out on your CV to state that the research position listed wasn’t simply washing dishes and so on.</p>
<p>The key here is what your letter writers have to say about your role in the research that led to the publication. They should explain exactly what you did and did not contribute to the publication - data analysis, lab tech work, writing, literature review, etc.</p>